“and whatever portion of it you recite from the Quran”—the pronoun may refer to Allah, for the Quran is from Him; or it may refer back to the affair just mentioned, that is: among those concerns is your recitation of the Quran.

“and none of you perform”—this addresses the entire ummah, the Messenger ﷺ included—

“any deed,” whether good or evil—

“except that We are witnesses over you,” seeing, perceiving, and observing you. This supports his ﷺ statement: “for He indeed sees you.”

“as you are engrossed in it,” meaning as you engage in it and carry it out. This establishes proof for the second rank of iḥsān: that He, majestic and exalted, is a Witness over every doer and every deed—He sees, knows, and observes him, and nothing escapes Him: “Indeed, nothing whatsoever is hidden from Allah in the earth or in the sky” [Āl ʿImrān: 5].

As for iḥsān between the servant and creation, it means extending kindness to them and withholding harm from them: feeding the hungry, clothing the naked, assisting the needy with your influence, interceding on behalf of those who need intercession—offering every form of good—honoring the guest, honoring the neighbor, so that nothing issues from you toward your neighbor except good, and you likewise withhold your harm from him.