It is narrated from Sayyiduna Bilal bin al-Harith (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "A man speaks a word that angers Allah, not knowing how far it has reached, and Allah, because of it, writes for him His displeasure until the day he meets Him. And a man speaks a word that pleases Allah, not knowing how far it has reached, and Allah, because of it, writes for him His pleasure until the day he meets Him."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1129