WEANING
The term "weaning" designates the period during which the mother begins giving the baby other foods in addition to breast milk and finally ceases nursing altogether. The normal age for weaning was set by some sages as twenty-four months, (Kettubot 60, Responsa Noda BeYehuda 142:20), however, others maintained that the infant was ready for solid foods at fifteen months.(Responsa Iggerot Moshe 2:6) As such long periods of nursing are not practiced in modern times, (since it is considered dangerous for the baby to go without solid foods for so long, a fact confirmed by Rabbi Feinstein, z"l), it is the practice for mothers to follow the advice given by the talmudic sage Samuel: the baby should nurse as long as he wants to. (Kettubot 60) If the child becomes ill at any point after weaning, it is the mother's responsibility to continue nursing it. This will help relieve the baby's illness.(Kettubot 60)
In biblical times, it was the custom to make a joyous feast on the occasion of weaning the child to give thanks to the Almighty that the child had survived the most perilous stage of infancy..This is learned from the feast prepared by Abraham on the occasion of his son's weaning. (Genesis 21:8) In talmudic times, it was the custom to celebrate the child's weaning any time from eighteen months to five years. (According to the school of Hillel, the child is weaned at eighteen months; according to Rabbi Eliezer, the child may nurse up to twenty-four months; according to Rabbi Joshua, a child should be allowed to nurse up to the age of five! (Kettubot 60)
Accordingly, we note that Samuel was weaned at the age of three, after which he was admitted into the services of the Temple.(I Samuel 1:24)