It is narrated from Sayyidah Umm Kulthum bint Uqbah (may Allah be pleased with her); she said: I heard the Messenger of Allah (peace and blessings be upon him) say: "The liar is not the one who makes peace between people, saying something good or conveying something good."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 21658