Sahih Muslim
The Book on Salutations and Greetings (Kitab As-Salam)
Book Number: 026 / Hadith Number: 5541
'Amr b. Sharid reported on the authority of his father that there was in the delegation of Thaqif a leper. Allah's Apostle (may peace be upon him) sent a message to him: We have accepted your allegiance, so you may go.