Musnad Abu Ya'la al-Mawsili 115:113

Nasr ibn Ali narrated to us, [saying] Nuh ibn Qays narrated to us, from his brother Khalid ibn Qays, from Qatadah, from Anas: That the Messenger of Allah (may Allah bless him and grant him peace) wrote to Chosroes, Caesar, and every tyrant, inviting them to Allah.