It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he said: When your Prophet (peace and blessings be upon him) was bowing or prostrating, he would say: 'Subhanaka wa bihamdika, astaghfiruka wa atubu ilayk' (O Allah, You are free of all imperfection, and with Your praise; I seek Your forgiveness and I turn to You in repentance).
No one narrated this hadith from Hammad (may Allah have mercy on him) except Zayd bin Abi Unaysah (may Allah have mercy on him), and from Zayd (may Allah have mercy on him) none except Ubaydullah bin Amr (may Allah have mercy on him); Abdullah bin Ja'far (may Allah have mercy on him) is alone in narrating it, and it is narrated from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) only with this chain.
Hadith Referenceالمعجم الأوسط / باب الألف / 394
Hadith Takhrij«أخرجه البزار فى «مسنده» برقم: 1970، والطبراني فى «الكبير» برقم: 10302»