Musnad Ahmad 32:2057

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Yahya ibn Abi Ishaq, who said: I asked Anas ibn Malik about prayer during travel. He said: We went out with the Messenger of Allah, may Allah bless him and grant him peace, from Medina, and we used to pray two rak‘ahs until we returned to Medina. I asked him: How long did you stay in Mecca? He said: Ten days. I said: And with what did the Messenger of Allah, may Allah bless him and grant him peace, enter into the state of ihram? He said: "At your service for an ‘Umrah and a Hajj."