In the discourse of the scholars, based on the Qur'an, there is an issue known as 'portents of the Hour' (ashrat al-sa'a) which refers to the signs preceding the Resurrection. These signs are divided into two types: (a) Events which occur before the Resurrection and the collapse of the created order; these events take place when people are still living on earth. The phrase 'portents of the Hour' refers, in the main, to this type of phenomenon. (b) Events which are the cause of the collapse of the created order, most of which are mentioned in the following Suras: al-Takwir (81), al-Infitar (82), al-Inshiqaq (84) and al-Zilzal (99).
The signs of the first type can be summarized as follows:
1. The raising up of the last Prophet (Sura Muhammad, 47:18).
2. The breaking up of the barriers, [hitherto restraining] Gog and Magog (Sura al-Kahf, 18: 97-99).
3. The covering over of the sky by thick smoke (Sura al-Dukhan,44:10-16).
4. The descent of the Messiah (Sura al-Zukhruf, 43:57-61).
5. The emergence of a beast from the belly of the earth (Sura al¬Naml, 27:82).
Explanation of these signs can be found in books of exegesis and Hadith.
As regards the signs of the second type, the Qur'an speaks in detail of the transformation of the existential conditions of the universe. The collapse of the sun, the moon, the oceans, the mountains, the earth and the sky; in sum, the existing order will be rolled up as a scroll, and a new order will arise, thus manifesting God's all-encompassing power, as it is said:
The Holy Qur'an describes an event named 'the blowing of the trumpet', which will occur twice: (a) the first blast of the trumpet causes the death of all living creatures in the heavens and the earth (except those for whom God wills otherwise); (b) the second blast will revive the dead and bring them all before God,  as it is said:
The Qur'an specifically says in regard to the gathering and the resurrecting of mankind on the Day of Judgement:
1. Therefore the verse: It will not be but one blast, and at once they are all brought present before Us.(Sura Ya Sin, 36:53), is a clarification of the reality of the blowing of the trumpet referred to in verse 51 of the same Sura, And the Horn will be blown; and at once from the graves to their Lord they will hasten. This verse means that the second blast of the trumpet is a 'shout', after which all will suddenly be brought before God.