Musnad Ahmad 27:225

Yahya narrated to us, from Ubaydullah, Sa’id ibn Abi Sa’id narrated to me, from Jurayj or Ibn Jurayj, who said: I said to Ibn Umar: "Four things I have seen you doing, which I have not seen anyone else doing." He said: "What are they?" He said: "I saw you wearing these Sabtiyyah sandals, and I saw you touching these two Yemeni corners [of the Kaaba] and not touching any others, and I saw you not beginning the Talbiyah until your foot was in the stirrup, and I saw you dyeing your beard yellow." He said: "As for my wearing these Sabtiyyah sandals, the Messenger of Allah (peace and blessings of Allah be upon him) used to wear them, perform ablution in them, and liked them. As for touching these two corners, I saw the Messenger of Allah (peace and blessings of Allah be upon him) touching them and not touching any others. As for my dyeing my beard yellow, I saw the Messenger of Allah (peace and blessings of Allah be upon him) dyeing his beard yellow. And as for my beginning the Talbiyah when my mount is steady with me, I saw the Messenger of Allah (peace and blessings of Allah be upon him), when he placed his foot in the stirrup and his mount was steady with him, he would begin the Talbiyah."