Musnad Ahmad 27:794

Waki’ narrated to us, Ibn Abi Dhi’b narrated to us, from Nafi’, from Ibn ‘Umar, and from al-Zuhri, from Salim, from Ibn ‘Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The person in the state of Ihram shall not wear a garment that has been touched by wars (a type of dye) or saffron."