SABBATH. The term used in the Qur’an for the Jewish Sabbath is Sabt سبتa corruption of the Hebrew Shabbath.
It occurs five times in the Qur’an:-
Surah ii. 61: “Ye know, too, those of you who transgressed on the Sabbath., and to whom We (God) said, Become scouted apes.”
Surah iv. 50: “Or curse you as We (God) cursed the Sabbath breakers.”
Surah iv. 158: “We (God) said to them (Israel), Break not the Sabbath.”
Surah vii. 168: “And ask them (the Jews) about the city that stood by the sea when it’s inhabitants broke the Sabbath; when their fish came to them appearing openly on their Sabbath-day, but not to them en the day when they kept no Sabbath.”
Surah xvi. 125: “The Sabbath was only ordained for those who differed about it.”
In explanation of these verses, the commentator, al-Baizawi relates the following traditions. Moses gave orders for the observance of the Day of Rest on Friday; but the Jews would not obey, and declared that they would observe Saturdays as it was on that day that God rested from creation, so it came to pass that “the Sabbath’ was ordained for those who differed about it.” But in the time of King David, certain people began to break the Sabbath by fishing in the Red Sea near the town of Ailah (Elath), and as a punishment they were turned into apes.
For an account of the Muslim Sabbath, see [FRIDAY.]

Based on Hughes, Dictionary of Islam