TT #44 · Parashas Noach · Third Aliyah · Passuk 8:22
So long as the earth endures, seedtime and harvest, cold and heat, summer and winter, day and night shall not cease.
Torah Temimah points to Sanhedrin 58b (Reish Lakish — a non-Jew who observes a full day of rest is liable).
E-Daf image — Sanhedrin 58b (size=3)
Shas / HebrewBooks PDF of the daf
English: “They shall not cease” — Reish Lakish said: A non-Jew who observes a full day of rest is liable to death, as it is said “day and night they shall not cease,” and the Master said: Their warning is their death penalty.
Custom (Noachide restriction derived from “lo yishbotu”).
A non-Jew is forbidden to observe a full day of complete rest; the continuous cycle of day and night is read as applying also to human labor.