The Quran

وَلَو يُؤاخِذُ اللَّهُ النّاسَ بِظُلمِهِم ما تَرَكَ عَلَيها مِن دابَّةٍ وَلٰكِن يُؤَخِّرُهُم إِلىٰ أَجَلٍ مُسَمًّى ۖ فَإِذا جاءَ أَجَلُهُم لا يَستَأخِرونَ ساعَةً ۖ وَلا يَستَقدِمونَ

Muhammad Asad

Now if God were to take men [immediately] to task for all the evil that they do [on earth], He would not leave a single living creature upon its face. However, He grants them respite until a term set [by Him]:¹ but when the end of their term approaches, they can neither delay it by a single moment, nor can they hasten it.²

Or: "known [only to Him]" - i.e., the period of their lives on earth, during which they may reflect and repent.
For my rendering of sa'ah as "a single moment", see surah 7, note 26.