Maliks Muwatta Book 056, Hadith Number 005.

Section : The Order to be Mindful in Speech.

Malik related to me from Muhammad ibn Amr ibn Alqama from his father from Bilal ibn al-Harith al-Muzani that the Messenger of Allah, may Allah bless him and grant him peace, said, "A man speaks what is pleasing to Allah and he does not suspect that it will have the result that it does, and Allah will write for him His good pleasure for it until the day when he meets Him. And a man speaks what excites the wrath of Allah and he does not suspect that it will have the result that it does, and Allah will write His wrath for him for it until the day when he meets Him."