﴿ عَنِ ٱلنَّبَإِ ٱلْعَظِيمِ ﴾

“About the awesome tiding [of resurrection],”

About the awesome tiding this is the explication of that ‘thing’; the interrogative is meant to emphasise its magnitude — this awesome tiding is the Qur’ān comprising news of the Resurrection and so on which the Prophet s brought —