The word "Allâh" signifies the dashing of their final hope. For the only recourse and solace for those smitten by disaster is Allâh's mercy, and when they come to earn His wrath that hope is extinguished.
The word "encompasses (muhîtun)" infers that those all-encompassing calamities are the works of the Most High's wrath. Just as the sky, clouds, thunder, and night are assaulting them from all six directions, so the Most High's wrath and His tribulations surround them. Moreover, the Most High's knowledge and power encompass all beings, and His command embraces all particles. So it is as though "encompasses" is declaiming at them: "They cannot pass beyond the regions of the heavens and earth," (see, 55:33) and "whithersoever you turn, there is the countenance of Allâh." (2:115)
"All those who deny the truth (bi'1-kâfirîn):" the [preposition] "bi-" prefixing this suggests that [the dissemblers] have happened upon the very thing they were fleeing from and have become the target for its arrows.
This latter phrase indicates that the image of those represented, that is, the dissemblers, is portrayed in the mirror of the parable. This is so that the listener's mind should not be diverted by the parable and he does not forget the aim. It also indicates that the parable and those portrayed in it are so similar they are virtually the same; the difference between them has almost faded away so they seem identical and reality and imagination have merged. The phrase also signifies the gloominess of their hearts, for their consciences torment them too with their faults and crimes. Those who receive requital for their crimes are not easy in their consciences.
Now the parts of the phrase: "The lightning well-nigh takes away their sight (Yakâdu al-barq yakhtafu absârahum)"
This is apparently unconnected [to the previous phrase and therefore] implies that the listener is asking: "Why don't they take advantage of the lightning to reduce the calamity of the darkness for themselves?" And he is told: "They are scared of its harm more than [wanting] its advantages."
By reason of its well-known property "well-nigh (yakâdu)" points to the loss of their sight, but for some reason they did not lose it completely.1
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1.Kâda yakâdu, means on the point of, almost, hardly.