﴿ وَجَعَلْنَا ٱلَّيْلَ وَٱلنَّهَارَ ءَايَتَيْنِ ۖ فَمَحَوْنَآ ءَايَةَ ٱلَّيْلِ وَجَعَلْنَآ ءَايَةَ ٱلنَّهَارِ مُبْصِرَةًۭ لِّتَبْتَغُوا۟ فَضْلًۭا مِّن رَّبِّكُمْ وَلِتَعْلَمُوا۟ عَدَدَ ٱلسِّنِينَ وَٱلْحِسَابَ ۚ وَكُلَّ شَىْءٍۢ فَصَّلْنَٰهُ تَفْصِيلًۭا ﴾

“And We have established the night and the day as two symbols; and thereupon We have effaced the symbol of night and set up [in its place] the light giving symbol of day, so that you might seek to obtain your Sustainer's bounty and be aware of the passing years and of the reckoning [that is bound to come]. For clearly, most clearly, have We spelt out everything!”

And We made the night and the day two signs both indicators of Our power. Then We effaced the sign of the night extinguishing its light with darkness so that you might repose therein the annexation āyata’layli ‘the sign of the night’ is explicative and made the sign of the day sight-giving in other words one in which it is possible to see because of the light; that you may seek therein bounty from your Lord by earning your livelihood and that you may know by both day and night the number of years and the reckoning of the times of the day and everything that might be needed We have detailed very distinctly We have explained clearly.