A man entered the mosque and prayed while the Messenger of Allah ﷺ watched him without our noticing. When he finished, he came over and greeted the Messenger of Allah ﷺ.The Prophet ﷺ said, "Go back and pray, for you have not prayed."So the man went back and prayed, then came to the Messenger of Allah ﷺ again. The Prophet ﷺ said, "Go back and pray, for you have not prayed." This happened two or three times.The man said, "By the One who has honored you, Messenger of Allah, I have tried my best, so teach me."He said, "When you stand to pray, perform your ablution well, then face the qiblah and say the takbir. Then recite, then bow and remain still in your bowing. Then rise until you are standing upright. Then prostrate until you are still in your prostration. Then rise until you are still in your sitting. Then prostrate until you are still in your prostration. Then rise. Then do likewise until you have finished your prayer."
أخبرنا قتيبة قال حدثنا الليث عن ابن عجلان
أن رجلا دخل المسجد فصلى ورسول الله ﷺ يرمقه ونحن لا نشعر فلما فرغ أقبل فسلم على رسول الله ﷺ فقال ارجع فصل فإنك لم تصل فرجع فصلى ثم أقبل إلى رسول الله ﷺ فقال ارجع فصل فإنك لم تصل مرتين أو ثلاثا فقال له الرجل والذي أكرمك يا رسول الله لقد جهدت فعلمني فقال إذا قمت تريد الصلاة فتوضأ فأحسن وضوءك ثم استقبل القبلة فكبر ثم اقرأ ثم اركع فاطمئن راكعا ثم ارفع حتى تعتدل قائما ثم اسجد حتى تطمئن ساجدا ثم ارفع حتى تطمئن قاعدا ثم اسجد حتى تطمئن ساجدا ثم ارفع ثم افعل كذلك حتى تفرغ من صلاتك
[sahih] Reported by Abu Dawud in the Book of Prayer, Chapter on the prayer of one who does not straighten his back in ruku and sujud, hadith no. 860, and Tirmidhi, hadith no. 302, and others, from the hadith of Ali bin Yahya through the same chain, as previously mentioned, hadith no. 1054, and it is also found in Al-Kubra, hadith no. 1236.