A person may utter a word pleasing to Allah, the Almighty, without considering it of any significance, and because of it Allah raises his ranks; and a person may utter a word displeasing to Allah, the Almighty, without considering it of any significance, and because of it he sinks down into Hellfire
Sahih/Authentic with its two versionsعن أبي هريرة، عن النبي صلى الله عليه وسلم قال: «إن العبد لَيَتَكَلَّمُ بالكلمة من رِضْوَانِ الله تعالى ما يُلْقِي لها بَالًا يَرْفَعُهُ الله بها درجاتٍ، وإن العبد لَيَتَكَلَّمُ بالكلمة من سَخَطِ الله تعالى لا يُلْقِي لها بَالًا يَهْوِي بها في جهنم». وعن أبي عبد الرحمن بلال بن الحارث المزني رضي الله عنه : أن رسول الله صلى الله عليه وسلم قال: «إن الرجل لَيَتَكَلَّمُ بالكلمة من رِضْوَانِ الله تعالى ما كان يظن أن تبلغ ما بَلَغَتْ يكتب الله له بها رِضْوَانَهُ إلى يوم يَلْقَاهُ، وإن الرجل لَيَتَكَلَّمُ بالكلمة من سَخَطِ الله ما كان يظن أن تبلغ ما بَلَغَتْ يكتب الله له بها سَخَطَهُ إلى يوم يَلْقَاهُ».
Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "A person may utter a word pleasing to Allah, the Almighty, without considering it of any significance, and because of it Allah raises his ranks; and a person may utter a word displeasing to Allah, the Almighty, without considering it of any significance, and because of it he sinks down into Hellfire." Abu ‘Abdur-Rahmān Bilāl ibn al-Hārith al-Muzani (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "A person may utter a word pleasing to Allah, the Almighty, and he does not think it will yield such a result, and because of it Allah writes for him His pleasure until the Day he will meet Him; and a person may utter a word displeasing to Allah, the Almighty, and he does not think it will yield such a result, and because of it Allah writes for him His displeasure until the Day he will meet Him."
Explanation
A person may speak a word which Allah, the Almighty, loves and is pleased with, like advising, directing, or teaching others, and he does not realize the level it reaches in terms of the pleasure of Allah, the Almighty, and because of that word Allah raises him to lofty ranks. Likewise, a person may speak a word that displeases Allah, such as backbiting, gossip, and slander, and it causes him to fall into Hellfire on the Day of Resurrection.
Source · Narrated by Ibn Majah - Narrated by Bukhari - Narrated by At-Termedhy - Narrated by Ahmad - Maalik
From the Hadith Encyclopedia (hadeethenc.com).