Thus, from what has preceded, it has become clear that opposing the unbelievers and refraining from imitating them is one of the high objectives of the Islamic Sharia. Accordingly, every Muslim—men and women alike—must observe this in all their affairs, and most especially in their modes of dress, in view of the specific texts dealing with that matter; only then is the seventh condition concerning a woman’s attire properly fulfilled.
Some people may suppose that this avoidance of imitation is a purely devotional requirement. It is not so; rather, its rationale is intelligible and its wisdom evident. The well-grounded scholars have established the close connection between the outward and the inward, and that the former exerts an influence on the latter: when the outer is good, the inner follows suit, and when the outer is bad, so too is the inner. A person may be unaware of this effect within himself, yet he readily observes it in others.
Shaykh al-Islam, may Allah have mercy on him, said (pp. 105–106):
“This is a fact attested to by both perception and experience. Indeed, when two men from the same town meet while they are abroad, a remarkable affection and harmony develops between them—even though, back in their own city, they were neither acquainted nor on friendly terms—because…"