It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that he said: "The first to accept Islam was Sayyiduna Abu Bakr (may Allah be pleased with him)."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Ubaydullah and Musa except Sayf, and no one narrated it from Sayf except al-Nadr bin Hammad."
Hadith Referenceالمعجم الأوسط / باب الميم / 8365
Hadith Gradingمحدثین:إسناده ضعيف، فيه غير واحد ضعيف
Hadith Takhrij«قال الهيثمي: فيه غير واحد ضعيف «مجمع الزوائد ومنبع الفوائد، ج 9، ص 43»»