(458) بَابُ مُنْتَهَى السَّلامِ
(sic) Abu'z-Zinad said, "Kharija (ibn Zayd ibn Thabit) used towrite on the letter of Zayd when he said the salam, 'Peace be upon you,Amir al-Mu'minin, and the mercy of Allah and His blessings and His forgivenessand the best of His prayers."
Reference: Al-Adab Al-Mufrad 1001b
In-book reference: Book 42, Hadith 38
English translation: Book 42, Hadith 1001