The fact that jurists such as Ahmad and others cite this hadith as evidence that a child becomes Muslim whenever he is taken captive separately from his parents does not entail that the parents’ making him a disbeliever means merely assigning him their religious status. Rather, their argument is that, since he is born upon the true religion, it is his parents who turn him away from it by altering his natural disposition. Whenever Muslims take him captive separately from them, there is no one there to change his religion. Since he was born upon the upright, monotheistic religion, he becomes Muslim because the grounds for this remain operative, with nothing to counteract them. If his parents made him an actual disbeliever without teaching or instruction, however, the captive child would have the same status as an actual disbeliever.
It is well known that an adult disbeliever does not become Muslim when Muslims take him captive, because he has actually become a disbeliever.
Thus, if a child who follows his parents’ status were an actual disbeliever, captivity would not bring him out of disbelief. It follows that the rulings governing disbelievers were applied to him in this world because he followed his parents’ status, not because he had actually become a disbeliever.
This is illustrated by the fact that, if disbelievers took him captive, his parents would not be with him, yet he would not become Muslim. In this case, he is a disbeliever under worldly rulings, even though his parents have not made him a Jew, a Christian, or a Magian.
It is therefore clear that the hadith means that the parents instil disbelief in him and teach it to him.
The Prophet, peace and blessings be upon him, mentioned parents because they are ordinarily the primary caregivers who raise children. Every young child necessarily has two parents, and they are the ones who raise him as long as they remain alive and able to do so. This is unlike cases in which they die or become unable to raise him because he is taken captive and separated from them, or for some other reason.