Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: When the Prophet (peace and blessings be upon him) went into prostration, he would say in his prostration: "My self and my thought have prostrated to You, and my heart has believed in You. I acknowledge Your favour upon me. This is my hand and what I have committed against myself."
Imam al-Bazzar recorded it; its narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2779