إِنَّمَا جُعِلَ ٱلسَّبْتُ عَلَى ٱلَّذِينَ ٱخْتَلَفُوا۟ فِيهِ وَإِنَّ رَبَّكَ لَيَحْكُمُ بَيْنَهُمْ يَوْمَ ٱلْقِيَٰمَةِ فِيمَا كَانُوا۟ فِيهِ يَخْتَلِفُونَ
Innamā juʿila'l-sabtu ʿala'lladhīna'khtalafū fīh, wa inna rabbaka la-yaḥkumu baynahum yawma'l-qiyāmati fīmā kānū fīhi yakhtalifūn
"The Sabbath was laid down only upon those who differed about it. And your Lord will judge between them on the Day of Resurrection concerning that over which they differed."
The root خ-ل-ف occurs three times in this one verse: ikhtalafū, yakhtalifūn, and the disagreement to which fīmā kānū fīhi attaches.
And the root had occurred earlier in the sūra: in the thirty-ninth verse (yakhtalifūna fīh), in the ninety-second (mā kuntum fīhi takhtalifūn), in the sixty-fourth (alladhi'khtalafū fīh). This is a repetition verifiable within the sūra.
And the work of this verse must be recorded: the verse ties the cause of a ruling to a disagreement, and leaves the settling of the disagreement to the hereafter. It thus arrives at the same place as the sūra's ب-ي-ن series.
سَبْت — root س-ب-ت: to cut off, to stop, to break off. Subāt occurs in the Qurʾān as a description of sleep (al-Nabaʾ 78/9; al-Furqān 25/47) and was treated at al-Furqān, 25/47. The same root is here the name of the weekly day of stopping.
I record this as an observation about the language: the picture in the root is the same in both — the cutting off of work. The one daily, the other weekly.
The Qurʾān touches on this subject in several places (al-Baqara 2/65, al-Aʿrāf 7/163 and al-Nisāʾ 4/154). No detail is entered into, because al-Naḥl's verse does not enter into it either: innamā juʿila'l-sabtu ʿala'lladhīna'khtalafū fīh — a single sentence.