Tafsir of Al-A'raf 7:7

"Then We shall surely relate to them" — it is said this means: [relate] to the messengers when they entrust the matter to His knowledge, the Exalted, and say, "We have no knowledge; indeed, You are the Knower of the unseen." Or, [it means to relate] to them and to those to whom they were sent, all of their states. It is narrated from Ibn Abbas that He will cause their book of deeds to speak against them.

"With knowledge"—that is, being knowledgeable of their manifest and hidden aspects, or [it means] with that which We know of them. The ba (in the first interpretation) denotes accompaniment (mulabasa), and the prepositional phrase serves as a circumstantial qualifier (hal) for the subject of "We shall relate." In the second interpretation, the ba is connected to the verb "relate."

"And We were never absent"—from them in any state whatsoever. The intent is complete encompassing of their states and actions, such that nothing of them escapes His knowledge, the Glorified. The sentence is either a circumstantial qualifier or an initiation to emphasize what preceded it.