Musnad Ahmad 27:1267

Ishaq ibn Isa narrated to us, Abdullah ibn Zayd ibn Aslam narrated to us, from his father, from Ibn Umar, that he used to dye his clothes and apply saffron oil. It was said to him: "Why do you dye your clothes and apply saffron oil?" He said: "Because I saw it as the most beloved of dyes to the Messenger of Allah, may Allah bless him and grant him peace; he would apply it and dye his clothes with it."