بَلِ ٱلَّذِينَ كَفَرُوا۟ فِى تَكْذِيبٍ · وَٱللَّهُ مِن وَرَآئِهِم مُّحِيطٌۢ
Bali'lladhīna kafarū fī takdhīb · Wa'llāhu min warāʾihim muḥīṭ "Rather, those who disbelieve are in a state of denial. And God encircles them from behind."
The seventeenth verse had asked a question: "Has the tidings of the armies come to you?" The nineteenth verse begins with بَلْ.
This is an unexpected transition. Bal conveys leaving the preceding sentence and moving to something else (iḍrāb).
What it does is this: the question was asked, the answer was not waited for. It is as though the addressee said "yes, it has come", and the verse goes on: "then the matter is not a lack of knowledge."
The particle فِى conveys containment: a vessel, a taking inside, an enclosing. It has been treated several times in this commentary — fī kabadin (al-Balad), fī khusrin (al-ʿAṣr), fī taḍlīl (al-Fīl).
In the section on Sūrat al-Fīl this was recorded of the structure: "the plot has been placed inside the state of coming to nothing; no blow has fallen on it from outside, it has fallen into a condition that surrounded it from beginning to end."
The same logic works here: denial is not an act but an element. A person does not deny from time to time; he stands inside the denial.
And the word is indefinite (with tanwīn): takdhībin — "a denial". The indefiniteness conveys magnification here: a denial hard to describe, whose bounds are not drawn.
تَكْذِيب is a verbal noun on the tafʿīl pattern. As was recorded in the section on al-Shams, this pattern conveys "declaring what another has said to be a lie" — not lying oneself.
مُحِيط — Root: ح-و-ط. The concrete sense of the root: to surround a thing, to build a wall around it. Ḥāʾiṭ — a wall; iḥāṭa — encircling; ḥiyāṭa — a surround.
This expression is worth dwelling on. The verse does not say "He has encircled them"; it says "He has encircled them from behind."
The explanation of the classical exegetes: the encircling is coming from the direction they least expect and cannot see. A person guards his front; he cannot guard his back.
وَأَمَّا مَنْ أُوتِىَ كِتَٰبَهُۥ وَرَآءَ ظَهْرِهِۦ — "But as for the one whose record is given him from behind his back…" (al-Inshiqāq 84/10)
In both sūras the side a person cannot see is the side from which the verdict comes. In the one the record is given from behind, in the other the encircling comes from behind.
One more observation: at the beginning of the sūra the wrongdoers were sitting around the fire. They had encircled a pit.
The encirclers were encircled. This is a second performance, with another word, of the "the watchers were watched" move of the ninth verse.
I offer this as my own reading; but that the sūra repeats this method of reversal in three separate words (qutila, ḥarīq, muḥīṭ) is a datum of the text.