All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
This verse was revealed in response to those who denied resurrection from among the Quraysh. Ibn Juzayy said in his Tafseer: "In the verse {But when it is said to them, "Beware of what is before you and what is behind you"} [Quran 36:45], the pronoun 'them' here refers to the people of the Quraysh." [Ibn Juzayy, Tafseer, 2/183]
Al-Qurtubi said in his Tafseer: "Allaah The Exalted says (what means): {And they say, "When is this promise, if you should be truthful?"} [Quran 36:48] This verse means that when it was said to them {"Beware of what is before you and what is behind you"}, they mockingly said: {When is this promise?} They said so mockingly, implying that such a promise would not be fulfilled. The following verse reads: {They do not await except one blast which will seize them while they are disputing.} [Quran 36:49] The verse means that they do not await except for the last blast, which is the blowing of the Trumpet by the angel Israafeel when the Last Hour begins while they are disputing over their worldly affairs. They will die in their very place, and this is the stunning blow."
The resurrection would take place afterwards, after the death of the addressees when the verse was revealed. Al-Qurtubi said that the warning in this context is to those who follow the example of those disbelievers among the Quraysh. He said: "Allaah The Exalted says about the disbelievers of the Quraysh, {They do not await except one blast which will seize them while they are disputing.} This verse refers to the disbelievers at the end of time who follow the example of Abu Jahl and his fellows. They are only waiting for the first blast, which will bring forth their destruction. It will seize them while they are disputing in their marketplaces and seeking after their worldly needs …” [At-Tathkirah bi-Ahwaal Al-Mawta wa Umoor Al-Aakhirah, p. 477]
It was also said that Allaah The Exalted did not answer their question but, rather, warned them of the gravity of their punishment in the Hereafter to stress the importance of preparing oneself for it. Ibn ‘Aashoor said: "They wait for nothing other than the Great Blast on the Day of Judgment that marks the end of the world. The second blow (of resurrection) will indicate the beginning of the eternal life in the Hereafter. The style of speech in the second verse is different from the speech in the first verse so as to indicate that Allaah did not answer their question because they were merely mocking. The answer to their mockery was informing them of the punishment that awaits them in the Hereafter.
"It is also possible that the verse refers to a literal scream, indicating the punishment in the worldly life. It may refer to the blasting scream of the person who came to inform the people of Quraysh that the Muslims had seized the trade caravan at the time of the Badr encounter." [At-Tahreer wat-Tanweer]
Allaah Knows best.