Our sages note several interesting connections between the biblical Book of Ruth and the festival of Shavuot:
a) Shavuot falls in the harvest season, and is defined by the Torah as the culmination of a seven-week count beginning with the first barley harvest; the story of Ruth unfolds against the background of the barley harvest in ancient Judea, with the mitzvah of leket (allowing the poor to "glean" the stalks that fall to the ground during the harvest) playing a pivotal role in the narrative.
b) Ruth is the ancestress of King David; David was born on the festival of Shavuot of the year 2854 from creation (907 BCE), and passed away on the same date 70 years later.
c) Ruth is the paradigm of the ger tzeddek, the "righteous convert" who with great sacrifice forsakes her or his former life and identity to be born anew as a Jew; in essence, however, we are all gerei tzeddek, having undergone that very process ourselves on the first Shavuot of history when we assembled at the foot of Mount Sinai to be born anew as G‑d's people.
The entire Book of Ruth is included in the Tikkun Leil Shavuot, the Torah digest studied on the night of the festival. In many communities it is publicly read in the course of the morning services on Shavuot day.
Now it came to pass in the days when the judges ruled, that there was a famine in the land. And a certain man of Bethlehem in Judah went to sojourn in the country of Moab, he and his wife, and his two sons. And the name of the man was Elimelech, and the name of his wife Naomi, and the names of his two sons, Machlon and Kilyon, Efratites from Bethlehem in Judah. And they came into the country of Moab, and remained there.
And Elimelech, Naomi's husband died; and she was left, and her two sons. And they took wives for themselves of the women of Moab; the name of the one was Orpah, and the name of the other Ruth; and they dwelled there about ten years. And Machlon and Kilyon died, both of them; so that the woman was bereft of her two sons and her husband.
Then she arose with her daughters in law, that she might return from the country of Moab; for she had heard in the country of Moab that G‑d had visited His people in giving them bread. So she went out of the place where she was, and her two daughters in law with her; and they took the road to return to the land of Judah.
And Naomi said to her two daughters in law: "Go, return each of you to her mother's house; and may G‑d deal loyally with you, as you have dealt with the dead, and with me. May G‑d grant you that you may find rest, each of you in the house of her husband." Then she kissed them; and they lifted up their voice, and wept.
And they said to her: "No, we will return with you to your people." And Naomi said: "Turn back, my daughters; why will you go with me? Are there yet any more sons in my womb, that they may be your husbands? Turn back, my daughters, go your way; for I am too old to have a husband. Even if I should say I have hope, even if I should have a husband tonight and should bear sons; would you tarry for them till they were grown? Would you, for them, refrain from having husbands? No, my daughters; for it grieves me much for your sakes that the hand of G‑d is gone out against me."
And they lifted up their voice, and wept again. And Orpah kissed her mother in law; but Ruth held fast to her.
And she said: "Behold, your sister in law has gone back to her people and to her gods; go back after your sister in law."
And Ruth said: "Entreat me not to leave you, or to return from following after you. Wherever you go, I will go; and where you lodge, I will lodge; your people shall be my people, and your G‑d my G‑d. Where you die, I will die, and there will I be buried; G‑d do so to me, and more also, if aught but death part you and me."
When she saw that she was steadfastly minded to go with her, then she left off speaking to her.
So the two of them went on until they came to Bethlehem. And it came to pass, when they were come to Bethlehem, that all the city was astir at their arrival, and they said: Is this Naomi? And she said to them, "Call me not Naomi ( 'pleasantness'); call me Marah ('bitterness"), for the Almighty has dealt very bitterly with me. I went out full, and G‑d has brought me back empty. Why then do you call me Naomi, seeing G‑d has testified against me, and the Almighty has afflicted me?"
So Naomi returned, and Ruth the Moabite woman, her daughter in law, with her, who returned out of the country of Moab; and they came to Bethlehem at the beginning of the barley harvest.
Now Naomi had a kinsman of her husband's, a man of wealth, of the family of Elimelech; and his name was Boaz.
And Ruth the Moabite said to Naomi: "Let me now go to the field, and glean ears of corn after him in whose sight I shall find favor." And she said to her: "Go, my daughter." And she went, and came, and gleaned in the field after the reapers; and she happened to come to a part of the field belonging to Boaz, who was of the kindred of Elimelech.
And, behold, Boaz came from Bethlehem, and said to the reapers, "G‑d be with you"; and they answered him, "G‑d, bless you." Then Boaz said to his servant that was set over the reapers: "Whose maiden is this?" And the servant that was set over the reapers answered and said: "It is the Moabite girl who came back with Naomi out of the country of Moab, and she said, 'I pray you, let me glean and gather after the reapers among the sheaves'; so she came, and has continued from the morning until now, scarcely spending any time in the hut."
Then said Boaz to Ruth: "Hearest you not, my daughter? Go not to glean in another field, nor go away from here, but keep close here to my maidens. Let your eyes be on the field that they reap, and go after them; have I not charged the young men that they shall not touch you? And when you are thirsty, go to the vessels, and drink of that which the young men have drawn."
Then she fell on her face, and bowed herself to the ground, and said to him: "Why have I found favor in your eyes, that you should take notice of me, seeing I am a stranger?" And Boaz answered and said to her: "It has been fully related to me all that you have done for your mother in law since the death of your husband; and how you have left your father and your mother, and the land of your birth, and have come to a people whom you knew not before. May G‑d recompense your deed, and may a full reward be given you by the L-rd, the G‑d of Israel, under whose wings you have come to take refuge."
And she said: "Let me find favor in your sight, my lord; for you have comforted me, and you have spoken gently to your handmaid, though I am not even like one of your handmaidens."
And Boaz said to her at the mealtime: "Come here, and eat of the bread, and dip your morsel in the vinegar." And she sat beside the reapers: and he reached her parched corn, and she did eat, and was replete, and left. And when she was risen up to glean, Boaz commanded his young men, saying: "Let her even glean among the sheaves, and do not reproach her; and let fall also some of the handfuls on purpose for her, and leave them, that she may glean them, and do not rebuke her." So she gleaned in the field until evening, and beat out what she had gleaned: and it was about an efah of barley.
And she took it up and went into the city, and her mother in law saw what she had gleaned; and she brought it out, and gave to her what she had left over after she had eaten her fill. And her mother in law said to her: "Where have you gleaned today, and where have you worked? Blessed is he who took notice of you." And she related to her mother-in-law where she had worked, and said: "The man's name where I worked today is Boaz."
And Naomi said to her daughter in law: "Blessed is he of G‑d, who has not left off his steadfast love to the living and to the dead." And Naomi said to her: "The man is near of kin to us, one of our nearest kinsmen."
And Ruth the Moabite said: "He said to me also: You shall keep close by my young men, until they have ended all my harvest." And Naomi said to Ruth her daughter in law: "It is good, my daughter, that you go out with his maidens, and that they meet you not in any other field." So she kept close to the maidens of Boaz to glean to the end of the barley harvest and of the wheat harvest; and dwelt with her mother in law.
Then Naomi her mother in law said to her: "My daughter, shall I not seek a home for you, that it may be well with you? And now is not Boaz of our kindred, with whose maidens you went?
"Behold, he winnows barley tonight in the threshingfloor. Wash yourself therefore, and anoint yourself, and put your raiment upon you, and get you down to the threshingfloor; but do not make yourself known to the man, until he has finished eating and drinking. And it shall be, when he lies down, that you shall mark the place where he shall lie, and you shall go in, and uncover his feet, and lay you down; and he will tell you what you shall do." And she said to her: "All that you say to me I will do." And she went down to the threshingfloor, and did according to all that her mother in law bade her.
And when Boaz had eaten and drunk, and his heart was merry, he went to lie down at the end of the heap of corn; and she came softly, and uncovered his feet, and laid herself down. And it came to pass at midnight, that the man was startled, and turned over; and, behold, a woman lay at his feet.
And he said: "Who are you?" And she answered: "I am Ruth your handmaid; spread therefore your skirt over your handmaid, for you are a near kinsman.
And he said: "Blessed be you of G‑d, my daughter; for you have shown more loyalty in the latter end than at the beginning, inasmuch as you did not follow the young men, whether poor or rich. And now, my daughter, fear not, I will do to you all that you require; for all the city of my people knows that you are a virtuous woman.
"Now it is true that I am your near kinsman; yet there is a kinsman nearer than I. Tarry this night, and it shall be in the morning, that if he will perform to you the part of a kinsman, good and well: let him do the kinsman's part; but if he will not do the part of a kinsman to you, then will I do the part of a kinsman to you, as G‑d lives. Lie down until the morning."
And she lay at his feet until the morning; and she rose up before one could recognize another person. And he said: "Let it not be known that a woman came into the threshingfloor." Also he said "Bring the veil that you have upon you, and hold it." And when she held it, he measured six measures of barley, and laid it on her; and he went into the city.
And when she came to her mother in law, she said: "Who are you, my daughter?" And she told her all that the man had done for her. And she said: "These six measures of barley he gave me; for he said to me, Do not go empty to your mother in law." Then she said: "Sit still, my daughter, until you know how the matter will fall; for the man will not rest quiet until he finishes the matter today."
Then Boaz went up to the gate, and sat down there; and, behold, the kinsman of whom Boaz spoke came by.
And he said: "Ho there, such and such a one! Turn aside, sit down here." And he turned aside, and sat down. And he took ten men of the elders of the city, and said: Sit down here. And they sat down.
And he said to the kinsman: "Naomi, who is come back out of the country of Moab, is selling a parcel of land, which was our brother Elimelech's; and I thought to advise you of it, saying: 'Buy it in the presence of the inhabitants, and in the presence of the elders of my people.' If you will redeem it, redeem it; but if you will not redeem it, then tell me, that I may know; for there is none to redeem it besides you, and I am after you." And he said: "I will redeem it."
Then said Boaz: "On the day you acquire the field from the hand of Naomi, you must acquire also from Ruth the Moabite, the wife of the dead, to raise up the name of the dead upon his inheritance." And the kinsman said: "I cannot redeem it for myself, lest I harm my own inheritance. Take my right of redemption for yourself, for I cannot redeem it."
Now this was the custom in former time in Israel concerning redeeming and concerning exchanging: to confirm all manner of transactions, a man pulled off his shoe, and gave it to his neighbor, and this was the manner of attesting in Israel. Therefore the kinsman said to Boaz, "Buy it for yourself," and drew off his shoe.
And Boaz said to the elders, and to all the people: "You are witnesses this day, that I have bought all that was Elimelech's, and all that was Kilyon's and Machlon's, from the hand of Naomi.
"Moreover, Ruth the Moabite, the wife of Machlon, have I acquired as my wife, to raise up the name of the dead upon his inheritance, that the name of the dead be not cut off from among his brethren, and from the gate of his place; you are witnesses this day."
And all the people that were in the gate, and the elders, said: "We are witnesses. May G‑d make the woman that is come into your house like Rachel and like Leah, which two did build the house of Israel; and be prosperous in Efrata, and be famous in Bethlehem. And may your house be like the house of Peretz, whom Tamar bore to Judah, of the seed which G‑d shall give you of this young woman."
So Boaz took Ruth, and she was his wife; and he went in to her, and G‑d gave her conception, and she bore a son.
And the women said to Naomi: "Blessed is G‑d, who has not left you this day without a redeemer, that his name may be famous in Israel. And he shall be to you a restorer of your life, and a nourisher of your old age; for your daughter in law, who loves you, who is better to you than seven sons, she has born him." And Naomi took the child, and laid it in her bosom, and became nurse to it.
And the women her neighbors gave it a name, saying: There is a son born to Naomi; and they called his name Oved--he is the father of Jesse the father of David.
Now these are the generations of Peretz: Peretz begot Hetzron. And Hetzron begot Ram, and Ram begot Amminadav. And Amminadav begot Nachshon, and Nachshon begot Salmah. And Salmon begot Boaz, and Boaz begot Oved. And Oved begot Jesse, and Jesse begot David.