Oneness, Uniqueness of Allah (Tawheed)
Ṣaḥīḥ al-Bukhārī 7541
بِسْمِ اللَّهِ الرَّحْمَنِ الرَّحِيمِ مِنْ مُحَمَّدٍ عَبْدِ اللَّهِ وَرَسُولِهِ إِلَى هِرَقْلَ، وَ{يَا أَهْلَ الْكِتَابِ تَعَالَوْا إِلَى كَلِمَةٍ سَوَاءٍ بَيْنَنَا وَبَيْنَكُمْ }
bismi-Llāh ar-raḥmani ar-raḥīmi min muḥammadin ʿabdi-Llāh warasūlihi ilā hiraqla, wayā ahla al-kitābi taʿālawā ilā kalimatin sawāʾin baynanā wabaynakum }
Transliteration generated from the Arabic vowel marks
The full narration
And Ibn 'Abbas narrated:Abu Sufyan bin Harb told me that Heraclius called for his translator and then asked for the letter of the Prophet (ﷺ), and the former read it (thus): "In the Name of Allah, the Most Gracious, the Merciful. (This letter is) from Muhammad bin 'Abdullah, to Heraclius. "...O people of the Scripture (Jews and Christians): Come to a word that is just between us and you that we worship none but Allah..." (V.3:)
Source
Ṣaḥīḥ al-Bukhārī · 7541
- Agreed upon as authentic (al-Bukhārī / Muslim)