Abu Ubaydah narrated: Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) passed by a man who had placed both his feet evenly together in the prayer, and he said: "This man has erred against the Sunnah; had he alternated his weight between his two feet, it would have been more beloved to me."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9314