Sahih Muslim
The Book Concerning the Use of Correct Words (Kitab Al-Alfaz min Al-Adab wa Ghairiha)
Book Number: 027 / Hadith Number: 5597
Abu Umama b. Sahl b. Hunaif, on the authority of his father, reported Allah's Messenger (may peace be upon him) as saying: None of you should say:" My soul has become evil," but he should say:" My soul has become remorseless."