The Prophet ﷺ used to begin his prayer with "In the name of Allah, the Most Gracious, the Most Merciful."
حدثنا أحمد بن عبدة الضبي حدثنا المعتمر بن سليمان قال حدثني إسمعيل بن حماد عن أبي خالد
كان النبي ﷺ يفتتح صلاته بـ بسم الله الرحمن الرحيم
No references are available.
[Its isnad is hasan]. Abu Dawud also reported it, as mentioned in Tuhfat Ashraf 5/265, hadith 6537, through the narration of Mutamir, with the same chain, and he said it is daif. Abu Khalid is Hurmuz Waalibi Kufi, whose hadith is hasan (Nayl Maqsud, hadith 1328). The hadith has many corroborating narrations. Ismail is the son of Hammad bin Abu Sulayman.