Al-Adab Al-Mufrad, Book 45, Hadith 4 (In-Book) ⓘ
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.
also referenced under: Hadith 1120 (Reference) & Book 45, Hadith 1120 (English)