Maliks Muwatta Book 20, Hadith Number 10.

Section : Wearing Clothes when in Ihram.

Yahya related to me from Malik from Nafi that he had heard Aslam, the mawla of Umar ibn al-Khattab, telling ‘Abdullah ibn Umar that Umar ibn al-Khattab once saw a dyed garment on Talha ibn Ubaydullah while he was in ihram and Umar said, “What is this dyed garment, Talha?”, and Talha said, “Amir al-muminin, it is only mud.” Umar said, “You and your like are taken by people as imams, and if an ignorant man were to see this garment he would say that Talha ibn Ubaydullah used to wear a dyed robe while he was in ihram. So do not wear any form of dyed clothes.”