Tafsir of An-Nur 24:17

An-Nur: (17) "Allah admonishes you that..."

"Allah admonishes you," meaning He counsels you, "that you never return to the like of it," meaning He expresses an aversion to your ever returning to it, or [the meaning is] "lest you return to it." Or, He admonishes you regarding the return—that is, regarding the matter of it and the sin and harm contained therein, just as one says, "I admonished him regarding wine and what it contains of harm." Alternatively, He restrains you from returning, by incorporating into the word "admonition" the meaning of restraint. It is said, "He returned to it," "he returned unto it," "he returned for it," and "he returned in it," all carrying the same meaning. The intent of "ever" is for the duration of one's life.

"If you are believers."

This is in the vein of the expression: "If I am a father to you, why do you not treat me well?" It contains a reminder to them of the faith which is the cause for refraining [from such acts], and it serves as an incitement to manifest that faith, framed in the form of a doubt. It also contains a hint of reproach.