Abdullah bin Ziyad al-Asadi narrates that he heard Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) saying while in the state of bowing (ruku'): "La hawla wa la quwwata illa billah (There is no power to avoid sin and no strength to do good except through Allah)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9174