She heard the Messenger of Allah ﷺ say, "The one who reconciles between people, conveying good or speaking good, is not a liar."
أنها سمعت رسول الله ﷺ يقول: ليس الكذاب الذي يصلح بين الناس، فينمي خيرا أو يقول خيرا.
Bukhari narrated it in the Book of Reconciliation (2692), and Muslim in the Book of Righteousness, Kindness to Relatives, and Manners (2605), both through the route of Salih, from Ibn Shihab, that Humayd bin Abdul-Rahman informed him, that his mother Umm Kulthum bint Uqba informed him, and he mentioned it. The wording given here is Bukhari's, and Muslim did not give the full text but instead referred to the hadith of Yunus from Ibn Shihab and said it was similar. He added in it, "she said, 'I never heard him permit falsehood in anything people say except in three cases'" following the same wording that Yunus attributed as a statement of Ibn Shihab, meaning his statement, "I never heard him permit falsehood in anything people describe as lying except in three matters, war, reconciling between people, and a man's speech to his wife and a woman's speech to her husband."The correct view is that this is from the speech of Zuhri, for it has been inserted into the hadith, as noted by Khatib in al-Fasl lil-Wasl al-Mudraj fi al-Naql (1/258–275), and by Daraqutni in his Ilal (15/358).Something of similar meaning was reported from Asma bint Yazid, who said, the Messenger of Allah ﷺ said, "Lying is not permitted except in three cases, a man speaking to his wife to please her, lying in war, and lying to reconcile between people." Tirmidhi (1939) and Ahmad (27570) both narrated it through the hadith of Abdullah bin Uthman bin Khuthaym, from Shahr bin Hawshab, from Asma bint Yazid, and he mentioned it.There is well known criticism of Shahr bin Hawshab, though his hadith is hasan when he does not become confused, and he became severely confused in this hadith. He narrated it once in this manner, another time as mursal without mentioning Asma, as Tirmidhi stated, a third time from Abu Hurairah, and a fourth time from Nawas bin Saman. The combination of these factors makes his hadith daif, and the view closer to correct is that it is mursal. And Allah, the Exalted, knows best.