Hadith: There is nothing heavier on the believer's scale on the Day of Judgment than good morals. Indeed, Allah detests the one who is indecent and foulmouthed

عَنْ أَبِي الدَّرْدَاءِ رضي الله عنه أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ:
«مَا شَيْءٌ أَثْقَلُ فِي مِيزَانِ الْمُؤْمِنِ يَوْمَ القِيَامَةِ مِنْ خُلُقٍ حَسَنٍ، وَإِنَّ اللَّهَ لَيُبْغِضُ الفَاحِشَ البَذِيءَ».
[صحيح] - [رواه أبو داود والترمذي] - [سنن الترمذي: 2002]

Abu ad-Dardā’ (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said:
"There is nothing heavier on the believer's scale on the Day of Judgment than good morals. Indeed, Allah detests the one who is indecent and foulmouthed."
[Authentic hadith] - [Narrated by Abu Daoud & At-Termedhy] - [Sunan At-Termedhy - 2002]

Explanation

The Prophet (may Allah's peace and blessings be upon him) informed that the heaviest thing, among deeds and sayings, on the believer's scale on the Day of Judgment is good morals represented in having a cheerful face, refraining from harming others and doing good to others. Allah Almighty hates the one who is ugly in his deeds and words, the foulmouthed who uses offensive language.