Musnad Ahmad 27:267

Yahya narrated to us, from Abd al-Malik, Sa'id ibn Jubayr narrated to us, that Ibn Umar said: "The Messenger of Allah (peace and blessings of Allah be upon him) used to pray upon his riding beast while coming from Makkah to Madinah, in whichever direction it faced with him. And concerning this, this verse was revealed: 'So wherever you turn, there is the Face of Allah' [Al-Baqarah: 115]."