Ruling on Underwear

Our shaykh ‘Abd al-Rahmaan al-Barraak answered this
question as follows:

“Underwear and other types of clothing have to do with habits
based on people’s traditions (‘urf), so long as they do not contradict the
sharee’ah. The wearing of pants (sirwaal) was known at the time of the Prophet
(peace and blessings of Allaah be upon him) because of the hadeeth of Ibn ‘Umar (may
Allaah be pleased with them both) concerning what the muhrim (person in a state of ihraam
for Hajj or ‘Umrah) is forbidden to wear: ‘The muhrim should not wear a shirt or
turban or pants…’ (Agreed upon).”

There is nothing wrong with wearing underwear so long as it does not
involve anything that is haraam, such as crosses or pictures of animate beings, or women
wearing men’s clothes and vice versa.