Bab Jibrīl (Gate no. 40)

This door, on the eastern side of Masjid-e-Nabwi is called Bab-e-Jibraeel because the angel Jibraeel (عليه السلام) [Angel Gabriel] used to descend from this side with the Wahi (revelation).

• Jibraeel (عليه السلام) came to the Prophet (ﷺ) after the battle of Ahzab (the battle of the Confederates and also known as the battle of the Trench), and talked to the Prophet (ﷺ) at the door step of Bab-e-Jibraeel.
• It is mentioned in Bukhari as narrated by Aisha (رضي الله عنه), “After the battle of Ahzab, the Prophet (ﷺ) disarmed himself and took a bath. In the meanwhile, Jibraeel (عليه السلام) came riding a pony and talked to the Prophet (ﷺ) near the door step of of Bab-e-Jibraeel. Jibraeel (عليه السلام) said to the Prophet (ﷺ), ‘You have put away your arms but we (the angels) are still in battle uniforms. So you should come with us to attack the tribe of Banu Quraizah’.” Aisha (رضي الله عنها) added, “I was looking at Jibraeel (عليه السلام) through the cracks in the door of my hut. Jibraeel (عليه السلام) was covered with dust.”
• This door is also known as Bab-e-Uthman (the Door of Uthman) as the Prophet  (ﷺ) used to go through it to visit Uthman (رضي الله عنه) whose house was opposite.
• Note that the original position of this door was further inside the present mosque. It was moved eastwards with the extension of Masjid-e-Nabwi.

References:  History of Madinah Munawwarah – Dr. Muhammad Ilyas Abdul Ghani