He caused fish to appear in their weirs on the Sabbath, but not on other days. If they had not set out their weirs on the Sabbath, this could not have occurred. In so doing, they dared God to punish them. At the same time, God tested their Sabbath observance by bringing fish only on that day. He would not have done so, had they been obedient.
Many people claim that Sabbath observance is impossible.
It has become impossible for them precisely because they have refused to observe it. In failing to observe it, they have lost the spiritual capacity to appreciate it. The last mention of the Sabbath is in chapter 16. Thy Lord will judge between them on the Day of Resurrection concerning that wherein they used to differ. The words penalty and punishment at the beginning of the ayat are supplied by the translators, because they are implied in the word ju ila .