Sirat p. 461 / Tabari VIII p. 27 http://realmuhammad.info/BanuQurayza.html
At the time of the noon prayers, Gabriel came to Muhammad wearing an embrodied turban and riding on a mule with a saddle covered with a piece of brocade.
He asked Muhammad if he had abandoned fighting, and when he said that he had, he said that the angels had not yet laid aside their arms, and that he had just come from pursuing the enemy. "Allah commands you, Oh Muhammad, to go to Banu Qurayza. I am about to go there to shake their stronghold."
Muhammad ordered it to be announced that none should perform the afternoon prayer until after he reached Banu Qurayza.
Muhammad sent Ali forward with this banner and the men hastened to it. Ali advanced until when he came near the forts, he heard insulting language used of Muhammad. He returned to meet Muhammad on the road and told him that it was not necessary for him to come near those rascals. Muhammad said: "Why? I think you must have heard them speaking ill of me," and when Ali said that it was so, he added: "If they saw me they would not talk in that fashion." When Muhammad approached their forts, he said: "You brothers of monkeys, has Allah disgraced you and brought his vengeance upon you?"
They replied: "Oh Abul-Qasim, you are not a barbarious person."
Muhammad 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 al-Kalbi 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."
Some of the men came after the last evening prayer, not having prayed the afternoon prayer because Muhammad had told them not to do so until he got to Banu Qurayza. They had been much occupied with warlike preparations and they refused to pray until they came to Banu Qurayza in accordance with his instructions, and they prayed the afternoon prayer there after the last evening prayer.
Allah did not blame them for that in His book, nor did Muhammad reproach them.