[1]. Allah’s Punishment is imminent and certain for the idolaters and the deniers, and the Day of Judgment is approaching.
[2]. Polytheism is associating partners with Allāh and the most grievous of all sins, as Allāh warned against it right after mentioning the imminence of the Hour of Doom. Allāh warns against idolatry and calls for pure and perfect monotheism in the two subsequent verses as well.
[3]. Allah's foremost undisputed sign of Power is that of creation, especially that of the largest humanly perceivable creations, the heavens and earth, over which none else is capable.
[4]. As soon as he becomes strong and independent.
[5]. I.e., the idolaters and the deniers who deny resurrection, argue against the Truth, and are ungrateful for Allah’s favors