One may not redeem either with slaves, with [loan] documents, or with land; and [similarly] not in the case of consecrated objects. [If] he wrote to a Kohen that he owes him five selaim, he is obligated to give [them to] him, but his son is not redeemed. Therefore, if the Kohen wishes to give him a gift, he may.  [If] one sets aside [money for] the redemption of his son and it is lost, he is responsible for it; as it states (Num. 18:15): It shall be yours, and you shall redeem.