Hadith 45:4
Sahih (Al-Albani)
Zayd ibn Aslam said, "My father sent me to Ibn 'Umar and I saw him write, 'In the Name of Allah, the All-Merciful, Most Merciful. Following on from that'"
حَدَّثَنَا قَبِيصَةُ، قَالَ: حَدَّثَنَا سُفْيَانُ، عَنْ زَيْدِ بْنِ أَسْلَمَ قَالَ: أَرْسَلَنِي أَبِي إِلَى ابْنِ عُمَرَ، فَرَأَيْتُهُ يَكْتُبُ: بِسْمِ اللهِ الرَّحْمَنِ الرَّحِيمِ، أَمَّا بَعْدُ
Original Reference: Al-Adab Al-Mufrad 1120