Sahih Muslim 2251
Sahih Muslim · Book 40: The Book Concerning the Use of Correct Words · It Is Disliked For A Man To Say: "Khabuthat Nafsi" (I Feel Bad)
Abu Umama b. Sahl b. Hunaif, on the authority of his father, reported Allah's Messenger (ﷺ) as saying:
وَحَدَّثَنِي أَبُو الطَّاهِرِ ، وَحَرْمَلَةُ ، قَالاَ أَخْبَرَنَا ابْنُ وَهْبٍ ، أَخْبَرَنِي يُونُسُ ، عَنِ ابْنِ، شِهَابٍ عَنْ أَبِي أُمَامَةَ بْنِ سَهْلِ بْنِ حُنَيْفٍ ، عَنْ أَبِيهِ ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " لاَ يَقُلْ أَحَدُكُمْ خَبُثَتْ نَفْسِي . وَلْيَقُلْ لَقِسَتْ نَفْسِي " .
None of you should say:" My soul has become evil," but he should say:" My soul has become remorseless."