(28) باب مَنْ أَمَرَ بِإِنْجَازِ الْوَعْدِ
Narrated `Abdullah bin `Abbas:
Abu Sufyan told me that Heraclius said to him, "When I inquired you what he (i.e. Muhammad) ordered you, you replied that he ordered you to establish the prayer, to speak the truth, to be chaste, to keep promises and to pay back trusts." Then Heraclius added, "These are really the qualities of a prophet."
Reference: Sahih al-Bukhari 2681
In-book reference: Book 52, Hadith 42
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 48, Hadith 846