I read the letter that the Messenger of Allah ﷺ wrote for Amr bin Hazm when he sent him to Najran. The letter was kept with Abu Bakr bin Hazm. The Messenger of Allah ﷺ wrote, "This is a declaration from Allah and His Messenger," then he wrote, "O you who believe, fulfill your contracts" [Maidah 5:1], and he wrote the verses that followed until he reached "Indeed, Allah is swift in reckoning" [Maidah 5:4]. Then he wrote, "This is the document concerning wounds. For a life, one hundred camels," and he continued in that manner.
أخبرنا أحمد بن عمرو بن السرح قال حدثنا ابن وهب قال أخبرني يونس بن يزيد
قرأت كتاب رسول الله ﷺ الذي كتب لعمرو بن حزم حين بعثه على نجران وكان الكتاب عند أبي بكر بن حزم فكتب رسول الله ﷺ هذا بيان من الله ورسوله {يا أيها الذين آمنوا أوفوا بالعقود} وكتب الآيات منها حتى بلغ {إن الله سريع الحساب} ثم كتب هذا كتاب الجراح في النفس مائة من الإبل نحوه
No references are available.
[Hasan] Abu Dawud narrated it in Maraseel, no. 257, from Ahmad bin Amr bin Sarh and others, with this wording. It is also found in Kubra, vol. 7060, and it represents a report from the book, which is also transmitted through another chain, see no. 4861 and others. The hadith has corroborating narrations.