Tafsir of Al-Inshiqaq 84:15

"Nay" (Bala) is an affirmative for what follows the negation (lan). His statement—Exalted is He—"Indeed, his Lord was ever of him Seeing" is a confirmation and an explanation for it. That is: Nay, he shall certainly return, for his Lord—Mighty and Majestic is He—who created him, was ever seeing of him and his deeds which necessitate recompense, such that nothing of them is hidden from Him—Glorified be He. Therefore, his return, his reckoning, and his requital are inevitable.