1309 – On the authority of Abū Hurayrah (may Allah be pleased with him) who said: The Messenger of Allah ﷺ stated, “When two people trade insults, the burden of whatever they utter falls upon the one who began, so long as the wronged party does not overstep the limit.” Recorded by Muslim ⦗1⦘.

Lexical notes
– al-mustabbān: with the b doubled; an active participle from the pattern of iftiʿāl. One says sābbahu musābbatan wa-sibāban, meaning “he reviled him.” Here it denotes the two persons who exchange insults.
– faʿalā al-bādiʾ: i.e., the sin rests upon the one who initiates the abuse, not upon the respondent who defends himself.
– mā lam yaʿtad: i.e., provided the aggrieved person does not go beyond the extent of the initiator’s insult.

Points derived from the hadith
1 – Reviling others is flagrant disobedience because it involves obscene, vulgar speech. Such wickedness may lead to even graver sins—shedding blood, stirring up turmoil—and at the very least it ignites enmity and hatred among Muslims. For that reason it is forbidden, for Allah detests the obscene and foul-mouthed.
2 – Whoever is wronged by insults is entitled to respond in kind, without adding anything beyond the original abuse. Allah the Exalted says, “If you retaliate, then retaliate with the like of that with which you were afflicted.” ⦗al-Naḥl 126⦘.
Yet superior to retaliation are forbearance, patience, and pardon: “But if you endure patiently, that is surely best for those who are patient.” ⦗al-Naḥl 126⦘; “So turn away with gracious forbearance.” ⦗al-Ḥijr 85⦘; and “Let them pardon and overlook—would you not love that Allah should forgive you?” ⦗al-Nūr 22⦘.