The digging of the trench lasted a few days and in this time they made arrangements of safe guarding themselves against the enemy. The enemy came and encircled the area. When the blockade had lasted twenty days, the Muslims were becoming some what worry of the siege, the treachery of the Jewish tribe Bani Quraizah and became quite troubled. At that time a soldier from among the unbelievers, Nu'aim bin Masood Nakha’ee who up to that time had not yet embraced Islam, but whose heart had already inclined towards truth, managed to drive a wedge between Quraish and the Jews, which averted the danger of them fighting the Muslims together. It so happened that while the unbelievers more still busy with the siege and blockade, a tremendous storm which destroyed the camp of the unbelievers, broke down their tents, so that their animals scattered in all directions with complete confusion spreading in all directions, so that they lifted the siege and fled. In this manner Allah saved the Muslims from this test.
At that moment Rasulullah (SM) remarked: "I have been helped and granted victory through the easterly wind and the people of Aad were destroyed by the westerly wind."
When Rasulullah (SM) needed someone to find out news about the enemy he asked three times: "Who will do this work for me?" And on three occasions Sayeduna Zubayr bin 'Owwaam offered himself for this task saying: "I am at your service for this duty." Then Rasul ullah said:
"Verily every prophet has a Lawaaree and my Lawaaree (disciple) is Zubair."
And at one occasion Rasulullah (SM) used to recite this Du'a:
"O Allah, Who revealed the Book, who is quick in taking account, defeat the Allies (who attack us) O Allah defeat them and make them shake." There is no God except Allah alone, who granted honour to His forces of Muslims and helped His servant and over powered the allies alone. And besides Him eveiything else will pass away."
This was that battle during which, because of their preoccupation with Jihad, the Asar Salah of Rasulullah (SM) and the Companions became Qadaa and at Maghrib time he performed both Salahs. (See Bukhari: Babul Jehad)
The Qur'an and the Battle of the Ahzaab
Hazrat A’isha (Ra) reports that the following verse was revealed in connection with the battle of the Ahzaab
Behold they came upon you from above you and from below you and behold the eyes became dim and the hearts gaped up to the throats, And you imagined various (vain) thoughts about Allah (SWT)." (33:10)
Because of this battle being mentioned in it, this Surah has been named Surah Ahzaab. In the second and third Rukoo, this battle is mentioned:
"O you who believe, remember the grace of Allah bestowed on you, when there came down on you hosts (to overwhole you), But we sent against them a hurricane and forces which you did not see. But Allah sees clearly all that you do.' (33:9-27)