Witnessing Archangel Jibraeel (Gabriel) (a.s)

Quran revealed through the medium of Archangel Jibraeel (Gabriel) (a.s) 
​
The majority of the Quran was revealed through the medium of Archangel Jibraeel (Gabriel) (alaihi salaam) as mentioned in one of its verse: “CONSIDER this unfolding [of God's message] (najm), as it comes down from on high! This fellow-man of yours has not gone astray, nor is he deluded, and neither does he speak out of his own desire: that [which he conveys to you] is but [a divine] inspiration with which he is being inspired - something that a very mighty one has imparted to him:”[1] The Arabic term 'najm' translated in the verse as 'unfolding' is generally understood to mean ‘star’ and that is how many English translators of the Quran have also translated this verse: "Consider Najm (Star) as it comes down". However in classical Arabic, 'najm' also means ‘arrival or coming of something gradually or in parts’, denoting the fact that the entire Quran was brought down gradually, in parts, to Prophet Muhammad ﷺ, one to four or five verses at a time, within a total of around 23 year time period. As for the wording “a very mighty one has imparted to him” is accepted by majority of Quran commentators to be referring to Jibraeel (Gabriel) (a.s) and this is due to the fact that he is the leader of angels and is one of mightiest of angels as also described to us in the following hadith: “the Prophet ﷺ had seen Gabriel (alaihi salaam) (in his actual appearance) with six hundred wings.”[2] The wings of the angels denote their power as confirmed in the Quran: “angels to be [His] message-bearers, endowed with wings, two, or three, or four.”[3] (please read as explained earlier) Jibraeel (Gabriel) (a.s) description having "six hundred wings" implies his mightiness in power whom Allah entrusted to bring down the revelation of the Quran including the first set of Surah 96 verses. 

Prophet Muhammad ﷺ would sometimes receive Archangel Jibraeel (Gabriel) (a.s) in his original form and sometimes in human form when receiving verses. The following incidents recorded in the hadith collections mention that Jibraeel (Gabriel) (a.s) as well other angels, came in human form and not only did they meet the Prophet ﷺ but also people around the Prophet ﷺ unknowingly witnessed their meeting. However they would usually find out later that it was an angel or angel Gabriel:

Hadith e Jibraeel (Tradition of Gabriel) - Jibraeel (Gabriel) in the form of a traveler 

The below is one of the famous traditions in Islam called the Hadith e Jibreel (Tradition of Gabriel) that happened a month before the Prophet ﷺ passed away. In this tradition angel Jibraeel (Gabriel) (a.s) appeared in the form of a man in the presence of the Prophet ﷺ and made inquiries about the deen (religion) so that those with him could observe the conversation and learn important lessons about Islam. Abdullah bin Umar (r.a) said:

Umar bin Al-Khattab (r.a) told me: 'While we were with the Messenger of Allah ﷺ one day, a man appeared before us whose clothes were exceedingly white and whose hair was exceedingly black. We could see no signs of travel on him, but none of us knew him. He came and sat before the Messenger of Allah, putting his knees against his, and placing his hands on his thighs, then he said: "O Muhammad, tell me about Islam." He said: "It is to bear witness that there is none worthy of worship except Allah ﷻ and that Muhammad ﷺ is the Messenger of Allah, to establish the Salah, to give Zakah, to fast Ramadan, and to perform Hajj to the House if you are able to bear the journey." He said: "You have spoken the truth." And we were amazed by his asking him, and then saying, "You have spoken the truth". Then he said: "Tell me about Faith." He said: "It is to believe in Allah (swt), His Angels, His Books, His Messengers, the Last Day, and in the Divine Decree, it’s good and it’s bad." He said: "You have spoken the truth." He said: "Tell me about Al-Ihsan." He said: "It is to worship Allah ﷻ as if you can see Him, for although you cannot see Him, He can see you." He said: "Tell me about the Hour." He said: "The one who is asked about it does not know more about it than the one who is asking." He said: "Then tell me about its signs." He said: "when a slave woman gives birth to her mistress, when you see the barefoot, naked, destitute shepherds competing in making tall buildings.'" Umar said: 'Three (days) passed, then the Messenger of Allah said to me: "O Umar, do you know who the questioner was?" I said: "Allah and His Messenger know best." He said: "That was Jibril, peace be upon him, who came to you to teach you your religion."[4]

One very important thing to note is that during the above incident the Muslim community in Madinah knew each other as it was very small town, it was unlike a metropolitan city of our times where many times people hardly even know who their neighbor is. If this man was not from Madinah then he must have traveled from outside. But to their surprise he did not have any traces of travel either even though traveling in deserts of Arabia was rough. Secondly this man is asking questions to the Prophet and every time the Prophet answers he replies in the affirmative. No man in the 23 years of Prophet Muhammad’s preaching had ever asked a question and after listening to the answer confirmed by saying ‘you have spoken the truth’. This is why the Companions said that they were amazed! Thirdly after the event was over the Prophet revealed that it was Angel Gabriel (alaihi salaam) who had come to revise their religious teachings and teach some important lessons.

Archangel Jibraeel (Gabriel) in Battle of Uhud

Another event recorded in the books of tradition that  Prophet Muhammad ﷺ in battle of Uhud was defended by the Angels which included Gabriel (a.s), and the companions saw this with their own eyes. This event happened when Muslims almost lost the battle and the enemies were on the offense and attacked the Prophet’s side. At that time Allah sent Angels for his assistance. It is recorded in Al Raheeq Al Maktum (The Sealed Nectar) that “In a version by Saad — cleared and authorized in Sahih Al-Bukhari and Muslim — he said: ‘I saw the Messenger of Allah (Peace be upon him) on Uhud Day with two men — dressed in white defending him fiercely — I have never seen similar to them neither before Uhud nor after it.” In another version: “He means to say that they were Gabriel and Michael.”[5] At this moment Madinah had much smaller community, for this incident took place in the early years of Prophet’s preaching in Madinah. These two men in white, defending the Prophet had never been seen by the companions before this event nor were they ever seen after.

Hamza (r.a) requested Prophet ﷺ to see Archangel Jibraeel (Gabriel) (a.s) in original form

Sheikh Said Al Nursi Bediuzzaman mentions in his work Miracles of Muhammad that Abu Sufyan bin Harith Abdul Muttalib, a cousin of the Prophet ﷺ, reports in an authentic narration that in the battle of Badr, they saw horsemen dressed in white between the sky and the earth. One day Hamza ibn Abdul Mutalib (radiAllahu anhu), the prophet's uncle, asked him that he wanted to see Jibraeel (Gabriel) (a.s). The Messenger ﷺ pointed towards the Kaabah, but Hamza (r.a) could not bear the sight and fell unconscious. (for more details please also see Malaikah - Energetic Beings of Nur (Light)​)

Archangel Jibraeel (Gabriel) (a.s) appeared in the form of Dihya Al Kalbi (r.a)

Angel Jibraeel Gabriel (a.s) also appeared in the form of a companion named Dihya Al Kalbi (r.a) who had a very handsome appearance. One of the wives of the Prophet, Umm Salamah (r.a) saw the Prophet ﷺ speaking to someone and heard what they discussed. Later the Prophet ﷺ summoned an audience and informed them of that knowledge which he said was just received from Gabriel (a.s). This amazed Umm Salamah (r.a) who till then was thinking whom she seen meet the Prophet was Dihya (r.a). Narrated Abu Uthman “I got the news that Gabriel came to the Prophet (ﷺ) while Umm Salamah was present. Gabriel started talking (to the Prophet (ﷺ) and then left. The Prophet (ﷺ) said to Umm Salamah, ‘(Do you know) who it was?’ (or a similar question). She said, ‘It was Dihya (a handsome person amongst the companions of the Prophet ﷺ.’ Later on Umm Salamah (r.a) said, ‘By Allah! I thought he was none but Dihya (r.a), till I heard the Prophet ﷺ talking about Gabriel in his sermon.'[6] 

References:
[1] Al Quran 53:1-5
[2] Jami Tirmidhi - Vol. 5, Book 44, Hadith 3278 
[3] Al Quran 35:01
[4] Sunan an-Nasa'i 4990
[5]  Al-Raheeq Al-Maktum – Chapter: Battle of Uhud – By Safiur Rahman Al Mubarakpuri
[6] Sahih al-Bukhari 4980