It is narrated from Sayyiduna Hajjaj (may Allah be pleased with him), he says: I said: O Messenger of Allah! What is it that can fulfill the right of the wet nurse from me? The Prophet (peace and blessings be upon him) said: A slave or a slave-girl.
Benefits: … By this right is not meant a wage; a wage is a separate matter, and giving a gift to the wet nurse (murdhi‘ah) at the time of weaning is a separate matter. From this hadith, it is understood that upon completion of the nursing period, the wet nurse should be given a slave man or slave woman as recompense for her favor—just as she carefully raised and nurtured the child, served him, and relieved the parents of this hardship, likewise, she should be given the gift of a soul (i.e., a slave man or woman) in return.