Tafsir of Al-`Ankabut 29:36

(And to Madyan) is connected to a suppressed verb "We sent," coordinated with "We sent" in the story of Nuh. And We sent to Madyan (their brother Shu‘ayb, so he said) to them, "O my people, worship Allah alone (and look forward to the Last Day); that is, expect it and what will occur within it of various terrors, and perform deeds today through which you may be secure from its consequences. Or, the command for expectation is a command to perform that upon which the expectation is dependent, placing the effect in the position of the cause. In the statement, there is a suppressed genitive construction (mudaf); the meaning is: perform that through which you hope for the reward of the Last Day. It is permitted not to assume a suppressed genitive, with the intention of reward being an instance of referring to a time by the events within it. It is also said: the command to hope for reward is a command to perform its causes, a requirement that involves no figurative language, based on the relationship of causality.

Abu Ubaydah said: "Hope" here bears the meaning of "fear." The meaning is: fear the recompense of the Last Day, from the vengeance of Allah Almighty upon you if you do not worship Him. (And do not commit abuse in the land, spreading corruption) is a confirmatory circumstantial qualifier (hal), because al-‘athw is corruption.