The Blowing of the Sur and the Day of Resurrection
It has been confirmed in a Hadith that the Messenger of Allah ﷺ was asked about the Sur and he replied,
«قَرْنٌ يُنْفَخُ فِيه»
(It is a horn that will be blown into.) It has been related in a Hadith about the Sur, on the authority of Abu Hurayrah that it is a huge horn that has a circumference as large as the heavens and the earth. The angel Israfil will blow into it. Another Hadith has been related which states that the Prophet said,
(How can I be comfortable when the one with the horn is holding it in his lips and his forehead is leaning forward, waiting to be given permission (to blow it).) The people said, "O Messenger of Allah, what should we say" He said,
يُنفَخُ فِي الصُّورِ (رضی The Day when the Horn الصُّورِ [ Sur ] will be blown - 20:102) According to Sayyidna Ibn ` Umar اللہ تعالیٰ عنہما ، a Bedouin الصُّورِ asked the Holy Prophet ﷺ about صُور (the Horn) to which he replied that it is something like a horn which will be blown, meaning thereby that when the angel will blow into it all those who had lain dead for centuries will return to life. Only Allah knows the true nature of the Sur (the Horn).
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 104–107
The fate which befell those who denied the truth brought into this world by the prophets was but a partial demonstration of God’s judgement, which will only fully unfold itself on the Day of Judgement and be applicable to all humanity. The Quran is a reminder of this very reality. When a person ignores the truth in this world, it seems to be a mere triviality, but in the Hereafter, this action of his will become a heavy burden upon him. When the divine trumpet (sur) announces that the period of trial is over, people will suddenly find themselves in another world. When it becomes clear to man that the world which he took to be his own was in fact God’s world, he will be so terror-stricken that his entire being will undergo a transformation, and his face will be a reflection of it. In the present world, man ignores the life hereafter, as if it were something very distant. But, after the advent of Doomsday, he will feel that the life of this world was nothing but a few numbered days, and the entire long life thereafter, stretching out before him into eternity, is the actual and ultimate reality.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.