﴿ إِنَّمَا جُعِلَ ٱلسَّبْتُ عَلَى ٱلَّذِينَ ٱخْتَلَفُوا۟ فِيهِ ۚ وَإِنَّ رَبَّكَ لَيَحْكُمُ بَيْنَهُمْ يَوْمَ ٱلْقِيَٰمَةِ فِيمَا كَانُوا۟ فِيهِ يَخْتَلِفُونَ ﴾

“[and know that the observance of] the Sabbath was ordained only for those who came to hold divergent views about him; but, verily, God will judge between them on Resurrection Day with regard to all on which they were wont to differ.”

The Sabbath was only prescribed in other words its consecration was made obligatory only for those who differed concerning it with their prophet — these were the Jews. They were commanded to devote themselves solely to worship on Friday but they said ‘We do not want it’ and chose Saturday; consequently thereon the observance of it was enforced strictly on them; and lo! your Lord will judge between them on the Day of Resurrection concerning that wherein they used to differ with regard this matter of the Sabbath by rewarding the obedient and chastising the one who disobeyed by his violating its sanctity.