Assalaamu alaikum,
I know that if a baby boy is completely breastfed without solid foods, his urine is pure, but what if he is formula fed instead of breastfed? would his urine be pure or is formula considered to be food?
Jazak Allah khair

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

The urine of the baby boy is not pure contrary to what the questioner said; most of the scholars said that it is impure, but the concession was made in the way of cleaning it. If the baby boy is formula fed, his urine is impure as well, but the question is: is it cleaned by just sprinkling water over it without washing as if the baby is breastfed? We have not found any text for contemporary scholars saying whether the formula is like the mother's milk so that it is not required to wash the urine of the formula-fed baby boy or if it is like food (and the ruling of the breast milk does not apply to it).

However, they discussed the milk of cattle. Some scholars stated the obligation of washing the urine of the baby boy who is fed on cattle milk, this was stated by some Shaafi’i jurists; others viewed the cattle milk as the mother's milk. In the collection of his Fataawa, Shaykh Muhammad ibn Ibraaheem commented on the meaning of 'the baby who has not eaten food', saying: “This means the baby boy whose food is only milk, whether the milk is breast milk or cattle milk. If the baby boy sucks or swallows what is put in his mouth, this is not considered as eating food. Also, when he desires food and it is not given to him, this is of no effect and thus his urine is not impure (i.e. it is not required to wash it). The same thing applies if he eats food without desire. To sum up, the baby boy who is considered as eating food is the one who wants food, eats it, longs for it, cries to have it or points at it, and hence the soup that they feed the baby is like all sorts of food. Allaah Knows best!”

However, taking precaution in the matters of worship necessitates washing the urine of the baby boy if he is formula fed, particularly since it could possibly not be pure milk of cattle.

Allaah Knows best.