912. Kapparos
131:1 The practice is to perform kapparos before dawn on the day before Yom Kippur, when G-d's attribute of mercy is greatest. A man uses a rooster - not a capon, which is castrated - and a woman uses a hen. A pregnant woman uses both a rooster and a hen - the rooster in case her baby is a boy and the hen in case it's a girl. If the baby is a girl, the one hen is sufficient for both the mother and the daughter. (Some say she should use a rooster and two hens - Mishnah Brurah 605:3.) Actually, any two people can share a chicken for kapparos (if their financial situation requires it - MB ibid.).
One should use a white chicken as per Isaiah 1:18, "If your sins are scarlet, they will become as white as snow." When one buys the chicken, he should not state his preference for a white one or pay a higher price for it, as this resembles an idolatrous practice. Rather, if one finds a white one among various chickens that he bought, then he should use it for kapparos.
Each person takes his chicken in his right hand and recites verses starting with Psalms 107:10, "Man, who dwells in darkness and the shadow of death...." He then swings the chicken around his head and says, "This is my substitute..." three times. If one swings the chicken around the head of another, he says, "This is your substitute...." One should swing it for himself first and then for others.
Preferably, the chicken should also be slaughtered before dawn, immediately after performing kapparos. A person should not be misled into thinking that this ceremony atones for him. Just the opposite, he should feel that he deserves that everything that happened to the chicken should have been done to him because of his sins; this should cause him to regret his sins so that G-d will accept his repentance. It is customary to throw the chicken's intestines, liver and kidneys on the roof or in a courtyard where the birds could take them. This would be an act of mercy on G-d's creatures in the hopes that He will show mercy on us. Another reason to discard these organs is that birds eat things they stole. By discarding these organs, we make a statement about distancing ourselves from theft.
If a chicken is not available, one may use a goose or any other animal that is unfit for use as a sacrifice. Some say that even fish may be used, but one may not use pigeons or doves. Since these are suitable for use as sacrifices, it would create the appearance of offering sacrifices outside the Temple.
Some have the practice to give the chickens to the poor. It is preferable to redeem the chickens for money and then to give the money to the poor. (The poor might be offended to be given a chicken upon which one has metaphorically placed his sins - Mishnah Brurah 605:5. Some perform the ceremony by swinging money around their head rather than a chicken; the money is then given to charity - MB 605:2. If one cannot ensure that the chickens will be treated properly, it may be advisable to use money.)
131:2 The following prayers are not recited on the day before Yom Kippur: Mizmor l'Todah (Psalm 100), Tachanun, and Lamnatzeiach (Psalm 20). Avinu Malkeinu is also not recited. When Yom Kippur falls on Shabbos, then we do say Avinu Malkeinu the day before, during shacharis.