I heard the Messenger of Allah ﷺ say, "One of you may utter a word that pleases Allah, never imagining it would reach what it reached, and Allah records His pleasure for him because of it until the Day he meets Him. And one of you may utter a word that angers Allah, never imagining it would reach what it reached, and Allah records His wrath against him because of it until the Day he meets Him."
حدثنا هناد حدثنا عبدة عن محمد بن عمرو حدثني أبي عن جدي قال سمعت
سمعت رسول الله ﷺ يقول إن أحدكم ليتكلم بالكلمة من رضوان الله ما يظن أن تبلغ ما بلغت فيكتب الله له بها رضوانه إلى يوم يلقاه وإن أحدكم ليتكلم بالكلمة من سخط الله ما يظن أن تبلغ ما بلغت فيكتب الله عليه بها سخطه إلى يوم يلقاه
[Its isnad is hasan]. Ibn Majah also narrated it in the Book of Tribulations, chapter on holding the tongue during tribulation, no. 3969, from the hadith of Muhammad bin Amr with the same wording. Hakim graded it sahih in 1/46, as did Ibn Hibban (al-Ihsan): 280, 287. The hadith of Malik is found in Muwatta, 2/985 (Yahya).