The six days between the festival of Sukkot and Shemini Atzeret (five in the Diaspora) and the five days between the first day of Pesach and the last day (four in the Diaspora) are referred to as chol ha-mo'ed.
The Sages, basing themselves on a number of verses in the Torah, ruled that work is forbidden on chol ha-mo'ed. However, the prohibition of work on chol ha-mo'ed differs from the prohibition on the Festivals which is specifically stated in the Torah. The definition of what constitutes forbidden work and what constitutes permitted work was given to the Sages to determine.
Any labor performed for the preparation of food - whether for oneself or for another - is permitted on chol ha-mo'ed.
Any form of non-strenuous work which would cause loss if not done at the time is permitted. However, work which could have been done before the Festival, and was deliberately delayed until chol ha-mo'ed, is forbidden.
If one had a certain type of work which he needed but was forbidden to perform by himself, and a poor person approached him and asked to be given work so that he might earn money with which to celebrate the Festival, one may allow the poor person to perform that work provided that he does so in private. (For example, one may give his laundry to a poor person to wash on chol ha-mo'ed - even in cases where he is prohibited to wash the laundry himself - so that the poor person can earn money.)
With the exception of essential watering and picking fruits needed for use during chol ha-mo'ed, all work in one's field is forbidden on chol ha-mo'ed unless refraining from performing it will cause great loss.
It is forbidden to cut one's hair or shave on chol ha-mo'ed. However, one who could not cut his hair before the Festival - e.g., a mourner or a person who was released from prison - may cut his hair.
One may cut his nails on chol ha-moed only if he also did so before the Festival. However, one may trim them with his teeth.
It is forbidden to wash clothes on chol ha-mo'ed unless the clothing is needed for the Festival and it was impossible to wash them beforehand. One is permitted to wash diapers.
Anything needed for medical purposes - whether for man or an animal - is permitted.
Business matters may not be recorded on chol ha-moed except if one fears that he might forget the details and a loss will thus result. Friendly correspondence which has no mention of business dealings may be written. However, one should write in a manner that is different.
If one borrows money - even if the money is not needed until after the Festival - one may write a promissory note. However, if he knows that he will be able to secure the loan after the Festival, he may not write a promissory note.
One may not move from one home to another on chol ha-moed unless the new home is in the same complex as the old. If one was living in a rented apartment and wishes to move into his own home, he is permitted to do so, for moving into one's own home is considered to be a source of joy.
Forms of work which are permitted on chol ha-moed should be performed only discreetly.
The purchase and sale of merchandise is forbidden on chol hamo'ed unless one of the following conditions applies:
- The money earned is necessary to provide for the needs of the Festival.
- One has an opportunity to earn a much larger profit than he would usually and he will thus be able to spend more for the Festival than would otherwise be possible.
- If one fails to sell now he stands to lose his capital. Loss of potential profit is not considered grounds to permit such transactions.
Weddings should not be held during chol ha-mo'ed, since one festive occasion should not be mixed with another. It is permissible, however, to become engaged to marry and to write the tena'im (binding terms of agreement between the two sides).
On chol ha-mo'ed, fasting and eulogizing the dead are forbidden. If a close relative dies (for whom one would sit shivah) on these days, one begins to observe the seven days of mourning only after the Festival, although private mourning practices are observed already on chol ha-mo'ed and Yom Tov.
One should be exceedingly careful not to perform any type of forbidden work. The Sages said: "One who treats chol ha-mo'ed lightly is considered to have worshiped idols" (Pesachim 118b). They also said: "One who treats the Festivals [including chol ha-mo'ed] lightly - even if he possesses Torah learning and good deeds -has no share in the World to Come" (Avot 3:15) Rather, one should honor chol ha-mo'ed and sanctify it by refraining from work, through good food and drink, and by wearing fine clothing.
On entering the house, one should greet the family with a holiday greeting: "Mo'adim 1'simchah" or "A good mo'ed," for this is part of the honor due to the occasion. To use the same greeting as on weekdays would be to "belittle" chol ha-mo'ed.
Some have a custom of lighting candles on every evening during chol ha-mo'ed as on Yom Tov.