Tafsir of Al-An'am 6:134

(Indeed, that which you are promised) means that which you are promised of the Resurrection, the Reckoning, the punishment, the reward, and the variation in degrees and ranks. The use of the future tense form is to indicate continuous renewal.

(What) is the noun of inna, and it is not permissible for it to be the kaffah (restrictive particle), because His saying, glory be to Him, (is coming) prevents that, as Abu al-Baqa' said. It is the predicate of inna, and the intent is that it will certainly come to pass without fail. The preference for "coming" (at) over "happening" (waqi') is to demonstrate the perfection of the speed of its occurrence, by portraying it in the form of an urgent seeker whom no fugitive can escape, just as His saying, the Almighty, expresses: (And you cannot cause failure) — meaning, you cannot make the One who seeks you unable to reach you or incapable of overtaking you.

Abu al-Shaykh narrated from Ibn Abbas, may Allah be pleased with them both, that the meaning is: "And you are not those who can outrun [Him]." The preference for the active participle form over the future tense is to signal the proximity of the coming, and the permanence conveyed by shifting from the verbal form to the nominal form is directed toward the negation; thus, the intent is the permanence of the negation of causing failure, not the explanation of the permanence of its negation, and it has parallels in the Noble Book.