Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
bayhaqi:20793 – my father

[Machine] The Messenger of Allah ﷺ said, "It is not appropriate for a truthful person to be foul-mouthed."  

البيهقي:٢٠٧٩٣ – حَدَّثَنَا أَبُو مُحَمَّدٍ عَبْدُ اللهِ بْنُ يُوسُفَ الْأَصْبَهَانِيُّ فِي آخَرِينَ قَالُوا ثنا أَبُو الْعَبَّاسِ مُحَمَّدُ بْنُ يَعْقُوبَ أنبأ الرَّبِيعُ بْنُ سُلَيْمَانَ أنبأ عَبْدُ اللهِ بْنُ وَهْبٍ أنبأ سُلَيْمَانُ بْنُ بِلَالٍ عَنِ الْعَلَاءِ بْنِ عَبْدِ الرَّحْمَنِ عَنْ أَبِيهِ عَنْ أَبِي هُرَيْرَةَ ؓ

أَنَّ رَسُولَ اللهِ ﷺ قَالَ لَا يَنْبَغِي لِصِدِّيقٍ أَنْ يَكُونَ لَعَّانًا  

رَوَاهُ مُسْلِمٌ فِي الصَّحِيحِ عَنْ هَارُونَ الْأَيْلِيِّ عَنِ ابْنِ وَهْبٍ

See similar narrations below:

Collected by Muslim
muslim:2597a – Hārūn b. Saʿīd al-Aylī > Ibn Wahb > Sulaymān Wahū Ibn Bilāl > al-ʿAlāʾ b. ʿAbd al-Raḥman from his father > Abū Hurayrah

It does not seem proper for a Siddiq that he should be an invoker of curse.  

مسلم:٢٥٩٧a – حَدَّثَنَا هَارُونُ بْنُ سَعِيدٍ الأَيْلِيُّ حَدَّثَنَا ابْنُ وَهْبٍ أَخْبَرَنِي سُلَيْمَانُ وَهُوَ ابْنُ بِلاَلٍ عَنِ الْعَلاَءِ بْنِ عَبْدِ الرَّحْمَنِ حَدَّثَهُ عَنْ أَبِيهِ عَنْ أَبِي هُرَيْرَةَ

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لاَ يَنْبَغِي لِصِدِّيقٍ أَنْ يَكُونَ لَعَّانًا