Tafsir of Al-Insan 76:27

"Indeed, these disbelievers love the immediate [life] and are engrossed in its fleeting pleasures, while they leave behind them—meaning, ahead of them—a heavy day, which is the Day of Resurrection. That it is 'ahead of them' is evident. Or, it means they cast behind their backs a heavy day which they do not concern themselves with. In the first interpretation, the adverbial phrase is a state (hal) of the 'day,' while in the second, it is an adverb of place for the verb 'they leave.' If it is construed uniformly in terms of attachment, that is also valid.

The day is described as 'heavy' by way of metaphor, likening its severity and burden to that of an arduous, burdensome object for its bearer. This sentence serves as a justification for what has been commanded and prohibited, as if it were said: 'Do not gratify them, but occupy yourself with what is more important regarding worship,' because they have abandoned the Hereafter for the sake of the worldly life; therefore, you abandon the worldly life and its people for the sake of the Hereafter.

It is also said that this provides a warning for those who love the immediate [life] and an encouragement for those who love the deferred [life]. The former is the reason for the prohibition against obeying the sinner and the disbeliever, while the latter is the reason for the command to worship."