Tafsir of An-Nur 24:12

{بأنفسهم} (By themselves): That is, by those among them who are believing men and believing women. It is like His saying: {And do not insult one another (yourselves)} [Al-Hujurat: 11].

This is similar to the report that Abu Ayyub al-Ansari said to Umm Ayyub, "Do you not see what is being said?" She replied, "If you were in Safwan’s place, would you think evil of the Prophet’s household?" He said, "No." She said, "And if I were in Aisha’s place, I would not have betrayed the Messenger of Allah (ﷺ). Aisha is better than me, and Safwan is better than you."

If you ask: Why was it not said, "Why, when you heard it, did you not think well of yourselves and say [it]?" Why was there a shift from address to the third person, and from a pronoun to an explicit noun?

I say: It is to intensify the rebuke through the method of iltifat (shift in address), and to explicitly state the word "faith" (al-iman). This indicates that sharing in faith necessitates that no believing man or woman should believe what is said about their brother or sister by an absent party or a slanderer.

It also serves as a reminder that when a believer hears a rumor about their brother, they should base their judgment on a positive assumption, not on doubt. They should say, with full conviction based on their good opinion of the believer: {This is a clear falsehood}. This is stated with the clarity of one who declares the other’s innocence, just as one who is certain and aware of the truth would speak.

This is a noble etiquette, though few are those who uphold it or preserve it. Would that you could find someone who, upon hearing such things, remains silent and does not spread what they have heard to others.

{Why did they not bring four witnesses for it? And since they did not bring the witnesses, then they, in the sight of Allah, are the liars.}