Why don’t we know for sure the exact night of Lailatu al-Qadr?

Allah kept the exact night of Lailatu al-Qadr a secret so that his servants would strive harder seeking it in all the final ten nights, just as he has made the exact time in which supplication is accepted every Friday unknown so that we would increase in our Du’a the whole day. He has also hidden from us his pleasure and acceptance of deeds so that we will seek his pleasure all of the time in his obedience. The time of our death and the exact time of the day of judgement are known only to Allah so that all people would strive to do their best all of the time and not wait until the end.

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