[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.