Sahih Muslim 2605 a
Humaid b. 'Abd al-Rahman b. 'Auf reported that his mother Umm Kulthum daughter of 'Uqba b. Abu Mu'ait, and she was one amongst the first emigrants who pledged allegiance to Allah's Apostle (ﷺ), as saying that she heard Allah's Messenger (ﷺ) as saying:
A liar is not one who tries to bring reconciliation amongst people and speaks good (in order to avert dispute), or he conveys good. Ibn Shihab said he did not hear that exemption was granted in anything what the people speak as lie but in three cases: in battle, for bringing reconciliation amongst persons and the narration of the words of the husband to his wife, and the narration of the words of a wife to her husband (in a twisted form in order to bring reconciliation between them).
حَدَّثَنِي حَرْمَلَةُ بْنُ يَحْيَى، أَخْبَرَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، أَخْبَرَنِي 
 حُمَيْدُ بْنُ عَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ، أَنَّ أُمَّهُ أُمَّ كُلْثُومٍ بِنْتَ عُقْبَةَ بْنِ أَبِي مُعَيْطٍ، وَكَانَتْ، مِنَ الْمُهَاجِرَاتِ
 الأُوَلِ اللاَّتِي بَايَعْنَ النَّبِيَّ صلى الله عليه وسلم أَخْبَرَتْهُ أَنَّهَا سَمِعَتْ رَسُولَ اللَّهِ صلى الله
 عليه وسلم وَهُوَ يَقُولُ ‏
"‏ لَيْسَ الْكَذَّابُ الَّذِي يُصْلِحُ بَيْنَ النَّاسِ وَيَقُولُ خَيْرًا وَيَنْمِي خَيْرًا
 ‏"‏ ‏.‏ قَالَ ابْنُ شِهَابٍ وَلَمْ أَسْمَعْ يُرَخَّصُ فِي شَىْءٍ مِمَّا يَقُولُ النَّاسُ كَذِبٌ إِلاَّ فِي ثَلاَثٍ
 الْحَرْبُ وَالإِصْلاَحُ بَيْنَ النَّاسِ وَحَدِيثُ الرَّجُلِ امْرَأَتَهُ وَحَدِيثُ الْمَرْأَةِ زَوْجَهَا ‏.‏