(4) باب الإحرام وما يتعلق به
Zaid bin Thabit (RAA) narrated, 'When the Messenger of Allah (ﷺ) intended to make Ihram for Hajj, he would wash, and take off his ordinary clothes (and put on his white Ihram)." Related by At-Tirmidhi who declared it to be Hadith-Hasan.
Reference: Bulugh al-Maram 730
In-book reference: Book 6, Hadith 23
English translation: Book 6, Hadith 749