Apparently, Muhammad used to mistake one of his companions, Dihya al-Qalbi, as the angel Jibril. Some people might say that Muhammad was the prophet of Dihya. Some people might say that the author of the Quran was Dihya because of Muhammad’s mistaken belief that Dihya was Jibril. But I won’t be so uncharitable.
Here is the evidence.
alinaam.org.za/library/rasul/ddminarets.htm
Bukhari as narrated by Aaisha [Radhiallaahu anha], ‘After the battle of Ahzaab, Prophet [Sallallaahu Alayhi Wasallam] disarmed himself and took a bath. In the meanwhile, Jibreel [Alayhis salaam] came riding a pony and talked to the Prophet [Sallallaahu Alayhi Wasallam] near the door step of Baab Jibreel. Jibreel [Alayhis salaam] said to the Prophet [Sallallaahu Alayhi Wasallam], ‘You have put away your arms but we (the angels) are still in battle uniforms. So you should come with us to attack Jewish tribe Banu Qurayza.’ Aaisha [Radhiallaahu anha] added, ‘I was looking at Jibreel [Alayhis salaam] through the cracks in the door of my hut. Jibreel [Alayhis salaam] was covered with dust.’
Prophet [Sallallaahu Alayhi Wasallam] asked people on his way to Banu Qurayza, ‘Did you see anybody pass this way a little while ago?’ They said, ‘We saw Dehya Qalbi pass this way riding a white and black pony. He had silk sheet spread under him.’ Prophet [Sallallaahu Alayhi Wasallam] said, ‘That was Jibreel [Alayhis salaam] who was sent to Banu Qurayza to destroy their forts and induce fear in their hearts.’
Sahih Bukhari
Volume 6, Book 61, Number 503:
Narrated Abu 'Uthman: I was informed that Gabriel came to the Prophet while Um Salama was with him. Gabriel started talking (to the Prophet). Then the Prophet asked Um Salama, “Who is this?” She replied, “He is Dihya (al-Kalbi).” When Gabriel had left, Um Salama said, “By Allah, I did not take him for anybody other than him (i.e. Dihya) till I heard the sermon of the Prophet wherein he informed about the news of Gabriel.” The subnarrator asked Abu 'Uthman: From whom have you heard that? Abu 'Uthman said: From Usama bin Zaid.
Volume 4, Book 56, Number 827:
Narrated Abu Uthman: I got the news that Gabriel came to the Prophet while Um Salama was present. Gabriel started talking (to the Prophet and then left. The Prophet said to Um Salama, “(Do you know) who it was?” (or a similar question). She said, “It was Dihya (a handsome person amongst the companions of the Prophet ).” Later on Um Salama said, “By Allah! I thought he was none but Dihya, till I heard the Prophet talking about Gabriel in his sermon.” (The Sub-narrator asked Abu 'Uthman, “From where have you heard this narration?” He replied, “From Usama bin Zaid.”)
Sahih Muslim Book 031, Number 6006:
Salman reported: In case it lies in your power don’t be one to enter the bazar first and the last to get out of that because there is a bustle and the standard of Satan is set there. He said: I was informed that Gabriel (Allah be pleased with him) came to Allah’s Apostle (may peace be upon him) and there was with him Umin Salama and he began to talk with him. He then stood up, whereupon Allah’s Apostle (may peace be upon him) said to Umm Salama: (Do you know) who was he and what did he say? She said: He was Dihya (Kalbi). He reported Umm Salama having said: By Allah, I did not deem him but only he (Dihya) until I heard the address of Allah’s Apostle (may peace be upon him) informing him about us. He (the narrator) said: I said to Uthman: From whom did you hear it? He said: From Usima b. Zaid.
So you see… the people of the time kept seeing Dihya but Muhammad only saw Jibril. Allah is most wise.