It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was in the mosque; then he related in detail the story of the man who did not perform the prayer well, until the Messenger of Allah (peace and blessings be upon him) taught him the prayer. In what the Messenger of Allah (peace and blessings be upon him) taught him there is also: "Then bow until you are at ease in bowing."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2569