How to write the beginning of a letter

'Abdullah ibn 'Umar wrote to 'Abdu'l-Malik ibn Marwan in order to pledge him his allegiance. He wrote to him, "In the Name of Allah, the All-Merciful, Most Merciful. To 'Abdu'l-Malik, the Amir al-Mu'minin, from 'Abdullah ibn 'Umar. Peace be upon you. I praise Allah to you. There is no god but Him. I offer you obedience according to the sunna of Allah and the sunna of His Messenger as much as I can."

حَدَّثَنَا إِسْمَاعِيلُ قَالَ: حَدَّثَنِي مَالِكٌ، عَنْ عَبْدِ اللهِ بْنِ دِينَارٍ، أَنَّ عَبْدَ اللهِ بْنَ عُمَرَ كَتَبَ إِلَى عَبْدِ الْمَلِكِ بْنِ مَرْوَانَ يُبَايِعُهُ، فَكَتَبَ إِلَيْهِ: بِسْمِ اللهِ الرَّحْمَنِ الرَّحِيمِ، لِعَبْدِ الْمَلِكِ أَمِيرِ الْمُؤْمِنِينَ مِنْ عَبْدِ اللهِ بْنِ عُمَرَ: سَلاَمٌ عَلَيْكَ، فَإِنِّي أَحْمَدُ إِلَيْكَ اللَّهَ الَّذِي لاَ إِلَهَ إِلاَّ هُوَ، وَأُقِرُّ لَكَ بِالسَّمْعِ وَالطَّاعَةِ عَلَى سُنَّةِ اللهِ وَسُنَّةِ رَسُولِهِ، فِيمَا اسْتَطَعْتُ.