What is the forbidden imitation (tashabbuh) in Islamic law? Does the prohibited imitation include the intention to imitate disbelievers, or does it apply to practices observed among disbelievers that Muslims adopt without the intention of imitating them, such as gradually shaving hair or lengthening it in a specific way?

The criterion for blameworthy imitation of disbelievers or transgressors is to imitate them in matters specific to them, in such a way that whoever sees the person would assume them to be one of them. Thus, a thing is not prohibited merely because disbelievers do it, if it is not exclusive to them. The measure of imitation is that the imitator does something that is specific to the imitated. As for something that has become widespread among Muslims and is no longer distinctive to disbelievers, it is not considered imitation.