of those who denied [the truth]," meaning: their end was that Allah destroyed them, then consigned them to the Fire.
"The command descends," meaning: the revelation, "between them," meaning: between the heaven and the earth, "so that you may know" by this revelation "that Allah is over all things competent and that Allah has encompassed all things in knowledge," for nothing escapes His knowledge.
Muhammad said: "Knowledge" is in the accusative case as an emphatic verbal noun (masdar mu'akkad), the meaning being: He has known everything with full knowledge. This part concludes with the praise of Allah.