The redemption ceremony (pidyon ha-ben) is held in the presence of the kohen and invited guests, and takes place on the 31st day after the birth. This is due to the fact that the child is not considered as fully viable until he survives the first 30 days of his life. Even if circumcision has not yet been performed (e.g., for health reasons), there should be no delay. Only if the 31st day is a Sabbath or festival is the ceremony postponed to the following weekday (ibid., 305:11). During the ceremony, the father presents his son, often on a specially embellished tray, to the kohen who asks him, in an ancient Aramaic formula, whether he wishes to redeem the child or to leave him to the kohen. In some sources the formula is given in Hebrew. The father, in reply, expresses the desire to keep his son, hands the redemption money to the kohen, and recites one benediction for the fulfillment of the commandment of redemption, and another of thanksgiving (She-Heḥeyanu). The kohen, three times pronouncing "your son is redeemed," returns the child to the father, This dialogue is purely symbolic. A declaration by the father that he prefers the money to the child would have no legal validity. Finally, the kohen recites a benediction over a cup of wine, pronounces the priestly blessing on the child, and joins the invited guests at a festive banquet (ibid. 305:10 and Isserles ad loc.).