Hajjaj b. Hajjaj al-Aslami quoted his father as saying, “Messenger of God, what will remove from me the obligation due for fostering a child.”* He replied, “A slave or a slave-girl of good quality.”
*It is said that Arabs liked to give a woman who had fostered a child something over and above the hire. This tradition deals with the amount to be considered full compensation for services rendered.
Tirmidhi, Abu Dawud, Nasa’i and Darimi transmitted it.