Jibreel in His Form
Multiple hadith narrations across al-Bukhari, Muslim, and other collections describe Jibreel (Gabriel) appearing to the Prophet in the form of Dihya al-Kalbi. The narrators explain: Jibreel, when taking human form, chose the form of the most beautiful man among the Companions.
This tradition is theologically significant: it grounds the Angel’s human appearance in an actual, known person among the community. Dihya’s companions could look at him and understand — in some approximation — what it had been like to see Jibreel’s human form.
Ambassador to Heraclius
In 6-7 AH, when the Prophet sent letters to the rulers of the known world inviting them to Islam, Dihya al-Kalbi was selected to carry the letter to Heraclius, the Emperor of Byzantium. The tradition records that Heraclius received Dihya with respect and that a conversation took place about the Prophet’s character.
The Byzantine account of Heraclius’s response — questioning Abu Sufyan ibn Harb (then still a non-Muslim) about the Prophet — is in al-Bukhari and forms one of the earliest “foreign witness” accounts of the Prophet in Islamic historical literature.
See also: Seerah Al Harith Ibn Abi Hala, Seerah Hudhayfah Ibn Al Yaman, Seerah Usama Ibn Zayd, Seerah Jafar Ibn Abi Talib, Ilm Al Sirah