It is narrated from Sayyidah Umm Kulthum bint Uqbah (may Allah be pleased with her), and she was among the first women who emigrated; she said: I heard the Messenger of Allah (peace and blessings be upon him) say: "He is not a liar who makes peace between people, saying something good or conveying something good."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21646