Bilal bin Harith (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Indeed, a person utters a good word and he does not realize its significance, yet because of it Allah writes His pleasure for him until the Day of Resurrection. And indeed, a person utters a bad word and he does not realize its importance, so because of it Allah writes His displeasure for him until the Day of Resurrection." Sharh al-Sunnah. And Imam Malik, Tirmidhi, and Ibn Majah have narrated a similar report. Its chain is Hasan. Narrated in Sharh al-Sunnah, Malik, Tirmidhi, and Ibn Majah.
Hadith Referenceمشكوة المصابيح / كتاب الآداب / 4833
Hadith Gradingالألبانی:لم تتمّ دراسته | زبیر علی زئی:إسناده حسن
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «إسناده حسن، رواه البغوي في شرح السنة (315/14 ح 4125) و مالک في الموطأ (985/2 ح 1914) و الترمذي (2319 وقال: حسن صحيح) و ابن ماجه (3969)»