Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: The Prophet (peace and blessings be upon him) used to recite "Bismillahir-Rahmanir-Rahim" aloud in prayer. (Allamah al-Haythami says:) I say: Abu Dawud and others have recorded this narration, but it does not mention reciting it aloud.
Al-Bazzar recorded it, and its narrators have been declared trustworthy.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2633
Hadith Gradingمحدثین:إسنادہ حسن
Hadith Takhrij«أخرجه المستدرك على الصحيحين برقم: 778»