We have to first understand the context of this incident, in order to understand it.
The circumstances suggest that it was Dihyah al-Kalbi, a companion of Muhammad, who first suggested him to blame Banu Qurayzah for betrayal, and then attack them for getting a lot of spoils of war and women. Muhammad also became ready for it, while he disliked the presence of the Jews in Medina.
But the problem was, there were only rumours, and Banu Qurayzah practically didn't betray Muslims during the whole Battle of the Trench. They neither killed nor wounded a single Muslim during the siege of Medina by the Meccans. Muslims were freely coming in and out of the area of Banu Qurayzah during that siege, which continued for one month (Sahih Bukhari, Hadith 3721).
Therefore, when Meccans ended the siege and returned to Mecca, the Muslims also put down their weapons and got busy in taking baths (neither of them blamed Banu Qurayzah for betrayal till that time, nor they felt any danger from them).
Muhammad also put down his weapons, and he was also bathing in the house of Umm Salama (one of his wives), when Dihyah al-Kalbi came to him, and suggested him to blame Banu Qurayzah and then attack them.
Muhammad also agreed upon it immediately, while it was a good EXCUSE for getting rid of the Jews of Medina. (Note: Muhammad had already previously successfully expelled the 2 large tribes of Jews, Banu Qaynuqa and Banu Nadhir, from Medina. And Banu Qurayzah were weaker and had no power to defeat Muslims alone)
Although Muhammad agreed to attack Banu Qurayzah, but still he needed a good EXCUSE to make his Jihadist companions ready too, to attack Banu Qurayzah. Thus, Muhammad again used revelation, and claimed that Jibril (i.e. Gabriel) came to him with Allah's order that Muslims should take up their weapons and attack Banu Qurayzah).
Ibn Kathir wrote under the commentary of verse 33:26:
... (after the Battle of the Trench) the Messenger of Allah returned to Al-Madinah in triumph and the people put down their weapons. While the Messenger of Allah was washing off the dust of battle in the house of Umm Salamah, may Allah be pleased with her, Jibril, upon him be peace, came to him wearing a turban of brocade, riding on a mule on which was a cloth of silk brocade. He said, "Have you put down your weapons, O Messenger of Allah'' He said, "Yes.'' He said, "But the angels have not put down their weapons. I have just now come back from pursuing the people.'' Then he said: "Allah, may He be blessed and exalted, commands you to get up and go to Banu Qurayzah (and attack them).'' According to another report, "What a fighter you are! Have you put down your weapons'' He said, "Yes.'' He said, "But we have not put down our weapons yet, get up and go to these people.'' He said: "Where'' He said, "Banu Qurayzah, for Allah has commanded me to shake them.'' So the Messenger of Allah got up immediately, and commanded the people to march towards Banu Qurayzah, who were a few miles from Al-Madinah. (Thus Muslims attack Banu Qurayzah, who went inside of their fort. The siege continued for 25 days. After that Banu Qurayzah had to lay down their weapons due to long siege, and noboday came to help them).
But who was that Jibril?
The problem occurred when people saw Dihyah coming out of the house of Umm Salama, while Muhammad claimed him to be Jibril.
Ibn Kathir further writes under the commentary of that same verse 33:26:
قالت فجاءه جبريل عليه السلام، وإن على ثناياه لنقع الغبار، فقال أوقد وضعت السلاح؟ لا والله ما وضعت الملائكة بعد السلاح، اخرج إلى بني قريظة فقاتلهم، قالت فلبس رسول الله صلى الله عليه وسلم لأمته، وأذن في الناس بالرحيل أن يخرجوا، فمر على بني تميم، وهم جيران المسجد، فقال " من مر بكم؟ " قالوا مر بنا دحية الكلبي، وكان دحية الكلبي يشبه لحيته وسنه ووجهه جبريل عليه الصلاة والسلام
Then came Jibril, whose face was full of dust. He said to the Prophet: "Have you put down your weapons'' He said, "Yes.'' He said, "But the angels have not put down their weapons. get up and go to Banu Qurayzah (and attack them)." So the Messenger of Allah got up immediately, and commanded the people to march towards Banu Qurayzah. The houses of the tribe of Banu Tamim were adjacent to the Mosque of the Messenger. Muhammad asked them if they saw anyone left from there? They told him that yes, they saw Dihyah al-Kalbi just left from there. But he was actually Jibril, whose beard and face resembled the beard and face of Dihyah al-Kalbi.
Umm Salama was confused. and she explained that confusion in her own words.
Narrated Abu `Uthman: I was informed that Gabriel came to the Prophet (ﷺ) while Um Salama was with him. Gabriel started talking (to the Prophet). Then the Prophet (ﷺ) 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 (ﷺ) wherein he informed about the news of Gabriel."
Moreover, Muhammad also claimed that Jibril was SHAKING the infrastructure of the fort of Banu Qurayzah. He claimed in order to encourage his Jihadist companions to attack Banu Qurayzah. Nevertheless, the fort of Banu Qurayzah stood there for the next 25 days, and it never shook. At the end, Banu Qurayzah had to lay down the weapons due to the shortage of food and water.
Sirah of Ibn Hisham, page 380 (link):
The apostle passed by a number of his companions in al-Saurayn before he got to Banu Qurayza and asked if anyone had passed them. They replied that Dihya b. Khalifa alKalbi had passed upon a white mule with a saddle covered with a piece of brocade. He said, 'That was Gabriel who has been sent to Banu Qurayza to shake their castles and strike terror to their hearts.'
It is impossible to refute these excuses, where revelation is also UNSEEN and where Jibril is also UNSEEN. Thus, even if people saw Dihyah instead of Jibril, then the new excuse is present that Jibril took the form of Dihyah.
Please ponder upon this question:
- Why did Jibril need to take the form of Dihyah and then come to Muhammad?
- Why was it not possible for Jibril to come to Muhammad in the UNSEEN form, as he always came to him?
- And when Umm Salama told Muhammad that he was Dihyah, why didn't he refute her on the spot and told her that he was actually Jibril in the form of Dihyah?
After Muhammad had slaughtered Banu Qurayzah, then there still remained a few small tribes of Jews in Medina. They were the tribe of Banu Haritha and Banu Salam etc.
But Muhammad also expelled them from Medina without even making any excuse (i.e. Muhammad didn't even take the pain of making any excuse and blaming them for anything, as he did previously in the case of 3 bigger tribes of Jews i.e. Banu Qaynuqa, Banu Nadhir and Banu Qurayzah). This time Muhammad expelled them even without blaming them for anything. Their only crime was that they didn't accept Muhammad to be the true prophet.
But Muhammad didn't stop expelling them from Medina. Later, when Muhammad got, even more, stronger, then he ordered to expel all Jews from the whole of the Arabian Peninsula (Sahih Muslim, 1767(a)).