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
quran:41:33 –

And who is better in speech than one who invites to Allah and does righteousness and says, "Indeed, I am of the Muslims."  

And who speaks better ˹words˺ — in other words, no one speaks better ˹words˺ — than him who summons ˹others˺ to God, by affirming His Oneness, and acts righteously and says, ‘Indeed I am one of those who submit ˹to God˺’?
القرآن:٤١:٣٣ –

وَمَنْ أَحْسَنُ قَوْلًا مِمَّنْ دَعَا إِلَى اللَّهِ وَعَمِلَ صَالِحًا وَقَالَ إِنَّنِي مِنَ الْمُسْلِمِينَ  

{ومن أحسن قولاً} أي لا أحد أحسن قولاً {ممن دعا إلى الله} بالتوحيد {وعمل صالحاً وقال إنني من المسلمين}.