بسم الله الرحمن الرحيم
This is prohibited due to the Prophet’s -sallahu alayhi wa salaam- statement to Abdullah ibn Amr ibnil Aws when he saw him wearing two garments dyed with safflower, “these are the garments of the disbelievers, do not wear them!” Collected by Muslim. Ahmad reports a narration with a good chain of transmission wherein the Prophet -sallahu alayhi wa salaam- said, “be at variance with the people of the book.” And it was said, “O Messenger of Allah! Indeed the people of the book wear the sirwal (a garment similar to pants) yet they do not wear the izar.” He -sallahu alayhi wa salaam- replied, “wear the sirwal along with the izar and differ with the people of the book.” Therefore the Muslim does not wear any clothing that are specific to the disbelievers.
Translated by Najeeb Al Anjelesi
Source: المنظار في بيان كثير من الأخطاء الشائعة