It is customary to give charity generously and liberally during all the days of repentance, but on the day before Yom Kippur this is even more the case, for tzedakah is a great source of merit and serves as protection against harsh decrees. Our Sages recount:
Mar Ukva was in the practice of giving four hundred zuz on every Erev Yom Kippur to a certain poor man who lived nearby. One year he sent the money with his son. His son came back and returned the money, saying: "Father, he has no need for charity."
Mar Ukva asked him: "What did you see [i.e., what made you reach this conclusion)?" He answered: "I saw that they were pouring vintage wine for him." Mar Ukva responded: "I didn't know that he was used to such delicacies!" He thereupon doubled the amount and sent him eight hundred zuz (Ketubbot 67b).
Plimo was wont to tease Satan [by never falling victim to his entreaties]. He would say: "An arrow in your eye, Satan!" One day, on Erev Yom Kippur, Satan appeared to him in the guise of a poor man. He approached Plimo's door and bread was brought out to him. He said: "On such a day, when everyone is dining at home I shall remain outside?"
They brought him in and served him bread. He said: "On such a day when everyone sits around the table, I should sit alone?" They set a place for him at the table. His entire body was covered with sores, which made him most repulsive, and he acted despicably. Plimo said to him: "Behave properly!" He said: "Pour me a cup of wine." They did so and he spat into it.
When they rebuked him he pretended to fall over, dead, and Plimo then heard a voice crying: "Plimo took a life, Plimo took a life!" Plimo fled and hid himself. When Satan saw his anguish and distress, Satan revealed his true identity (Kiddushin 81 a).