Sahih al-Bukhari 6478
Sahih al-Bukhari · Book 81: To make the Heart Tender (Ar-Riqaq) · To protect one's tongue
Narrated Abu Huraira:
حَدَّثَنِي عَبْدُ اللَّهِ بْنُ مُنِيرٍ ، سَمِعَ أَبَا النَّضْرِ ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ عَبْدِ اللَّهِ ـ يَعْنِي ابْنَ دِينَارٍ ـ عَنْ أَبِيهِ ، عَنْ أَبِي صَالِحٍ ، عَنْ أَبِي هُرَيْرَةَ ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " إِنَّ الْعَبْدَ لَيَتَكَلَّمُ بِالْكَلِمَةِ مِنْ رِضْوَانِ اللَّهِ لاَ يُلْقِي لَهَا بَالاً، يَرْفَعُ اللَّهُ بِهَا دَرَجَاتٍ، وَإِنَّ الْعَبْدَ لَيَتَكَلَّمُ بِالْكَلِمَةِ مِنْ سَخَطِ اللَّهِ لاَ يُلْقِي لَهَا بَالاً يَهْوِي بِهَا فِي جَهَنَّمَ " .
The Prophet; said, "A slave (of Allah) may utter a word which pleases Allah without giving it much importance, and because of that Allah will raise him to degrees (of reward): a slave (of Allah) may utter a word (carelessly) which displeases Allah without thinking of its gravity and because of that he will be thrown into the Hell-Fire."