It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both); he said: "The Messenger of Allah (peace and blessings be upon him) set out from Madinah towards Makkah, though he (peace and blessings be upon him) feared no one but Allah, and he kept praying two rak'ahs until he had left."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12807