﴿ وَنُفِخَ فِى ٱلصُّورِ ۚ ذَٰلِكَ يَوْمُ ٱلْوَعِيدِ ﴾

“and [in the end] the trumpet [of resurrection] will be blown: that will be the Day of a warning fulfilled.”

And the Trumpet will be blown for resurrection. That namely the day of the blast is the Day of the Promised Threat of chastisement for the disbelievers.