Musnad Abu Ya'la al-Mawsili 2:43

Ubayd Allah ibn Umar narrated to us, Yahya narrated to us, from Ibn Jurayj, Sulayman ibn Atiq narrated to me, from Abdullah ibn Abihi, from Ya'la ibn Umayyah, who said: I performed Tawaf with Umar ibn al-Khattab. When we were at the third corner, which is the one next to the Hijr or the chambers that are next to the door, I took his hand to touch it [the corner]. He said, "Did you not perform Tawaf with the Messenger of Allah (may Allah bless him and grant him peace)?" I said, "Yes." He said, "Did you see him touch it?" I said, "No." He said, "Then move on, for you have a good example in the Messenger of Allah."