Sayyiduna Bilal bin al-Harith (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "A man speaks a word that pleases Allah, not even imagining how far it has reached, and Allah, because of it, writes for him His pleasure until the day he meets Him. And a man speaks a word that angers Allah, not even imagining how far it will reach, and Allah, because of it, writes against him His displeasure until the day he meets Him."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1127