When the Soor is blown
The Messenger (sal Allahu alaihi wa sallam) said, “Then the Soor will be blown and no one will hear it but will tilt his head. The first one to hear it will be a man who will be fixing the trough for his camels. He will fall unconscious and people will also fall unconscious. Then Allah will send down rain or shade (Nu’maan ibn Saalim, a narrator was uncertain which one) which will cause the bodies of the people to grow. Then the Soor will be blown a second time, and they will be standing, looking on.”
As many ayaat and ahadith inform us (including the above hadith) that the Angel Israafeel will blow the Trumpet two times: the first will cause all creatures to fall unconscious, and the second will bring about the Resurrection.
Allah Says: And the Trumpet will be blown, and all who are in the heavens and all who are on the earth will swoon away, except him whom Allâh wills. Then it will blown a second time and behold, they will be standing, looking on (waiting). (Az-Zumar [39:68])
The Qur’an calls the first blast of the Trumpet Ar-Raajifah, and the second Ar-Raadifah. Allah says: On the Day (when the first blowing of the Trumpet is blown), the earth and the mountains will shake violently (and everybody will die), The second blowing of the Trumpet follows it (and everybody will be resurected)… (An-Naziat [79:6-7])
Elsewhere in the Qur’an the first blast is called As-Sayhah, and the idea of blowing into the Trumpet is clearly mentioned in the second case. Allah says: They await only but a single Sayhah (shout), which will seize them while they are disputing! Then they will not be able to make bequest, nor they will return to their family. And the Trumpet will be blown (i.e. the second blowing) and behold from the graves they will come out quickly to their Lord. (Ya Seen [36: 49-51])
And Allah knows best!