التفسير التبليغي
(Indeed, I thought that I would meet my account.) (20)
﴿إِنِّي ظَنَنْتُ﴾ meaning: I knew ﴿أَنِّي مُلَاقٍ حِسَابِيَهْ﴾ meaning: I would meet my recompense on the Day of Resurrection. That is, I prepared for it by striving diligently.
﴿ظَنَنْتُ﴾ its meaning here is: I was certain. The word 'dhann' (ظن) is used to mean certainty.
Based on this certainty, I used to strive for the establishment of religion within the Ummah and for all humanity.
Al-Dahhak said: Every instance of 'dhann' (ظن) in the Quran from a believer signifies certainty, and from a disbeliever, it signifies doubt. Mujahid said: The 'dhann' concerning the Hereafter is certainty, and the 'dhann' concerning this world is doubt. Al-Hasan said regarding this verse: Indeed, the believer had a good 'dhann' (thought/expectation) of his Lord, so he performed good deeds. And indeed, the hypocrite had a bad 'dhann' of his Lord, so he performed bad deeds.
﴿أَنِّي مُلَاقٍ حِسَابِيَهْ﴾ meaning: that I would be held accountable in the Hereafter.
Source: التفسير التبليغي