The preparation of food on Shabbat can entail the performance of prohibited labor. For children in general and infants in particular, the Sages were lenient and permitted the performance of certain essential activities.

It is prohibited to pump breast milk into a container on Shabbat if there is no special need. If the baby will not nurse and therefore the mother needs to pump milk to feed him, she should consult with a rabbi about how to do this on Shabbat. A woman suffering from engorgement at a time when the baby does not want to eat may express the milk but only if it becomes immediately unusable. Thus, she may express the milk directly into a sink or into a bottle that has soap in it.

Any food that can be prepared before Shabbat must be prepared in advance. Food that one cannot prepare before Shabbat, such as baby cereal and baby formula, may be prepared on Shabbat, but this should be done as follows:

To prepare formula from powder, one should pour the hot water from a secondary vessel (as defined in the chapter dealing with the kitchen and food on Shabbat, p. 419) onto the powder.

Baby cereal should be prepared by putting the powder into water that is in a secondary vessel. It is also preferable to make the cereal with a liquid consistency, rather than thick. If necessary, it is permitted to make thick cereal, but one should not stir the cereal in the normal way. Rather, one may mix the contents with distinct vertical and horizontal movements.

If it is necessary to warm cold milk or any other cold food which has already been fully cooked for a baby, one may place it in warm water in a secondary vessel. Alternatively, it may be placed near, but not on, a source of heat such as an electric hot plate, such that it will get warm but not reach the temperature of yad soledet bo (45° C, or 113° F).