Musannaf Ibn Abi Shayba 36:18

Khalid ibn Makhlad narrated to us, he said: Sulayman ibn Bilal narrated to us, he said: Rabi'ah ibn Abi Abd al-Rahman narrated to me, he said: I heard Anas ibn Malik saying: The Prophet, may Allah bless him and grant him peace, was sent [as a messenger] at the age of forty. He stayed in Makkah for ten [years] and in Al-Madinah for ten [years]. He passed away at the age of sixty.