A paternal uncle of his who was present at Badr told him, that a man entered the masjid and prayed, and the Messenger of Allah ﷺ was watching, but we did not realize. When he had finished, he came and greeted the Messenger of Allah ﷺ with salam. He said: "Go back and pray, for you have not prayed." So he went back and prayed, then he came to the Messenger of Allah ﷺ and he said: "Go back and pray, for you have not prayed." (This happened) two or three times. Then the man said to him: "By the One who has honored you , O Messenger of Allah ﷺ, I have tried my best; teach me." He said: "When you get up to pray, perform wudu and do it well, then turn to face the Qiblah and say the takbir. Then recite the Quran, then bow until you are at ease in bowing. Then stand up until you are standing straight, then prostrate until you are at ease prostrating, then sit up until you are at ease sitting, then prostrate until you are at ease prostrating, then get up, and continue doing that until you have finished your prayer." (Using translation from Nasāʾī 1313)
أَنَّ رَجُلًا دَخَلَ الْمَسْجِدَ فَصَلَّى وَرَسُولُ اللهِ ﷺ يَرْمُقُهُ وَهُوَ لَا يَشْعُرُ فَلَمَّا فَرَغَ أَقْبَلَ فَسَلَّمَ عَلَى رَسُولِ اللهِ ﷺ فَقَالَ لَهُ «ارْجِعْ فَصَلِّ فَإِنَّكَ لَمْ تُصَلِّ» فَرَجَعَ فَصَلَّى ثُمَّ أَقْبَلَ إِلَى رَسُولِ اللهِ ﷺ فَقَالَ لَهُ «ارْجِعْ فَصَلِّ فَإِنَّكَ لَمْ تُصَلِّ» فَرَجَعَ فَصَلَّى مَرَّتَيْنِ أَوْ ثَلَاثًا قَالَ الرَّجُلُ وَالَّذِي أَكْرَمَكَ يَا رَسُولَ اللهِ لَقَدْ جَهَدْتُ فَعَلِّمْنِي قَالَ لَهُ «إِذَا قُمْتَ تُرِيدُ الصَّلَاةَ فَتَوَضَّأْ فَأَحْسِنْ وُضُوءَكَ ثُمَّ اسْتَقْبِلِ الْقِبْلَةَ ثُمَّ اقْرَأْ ثُمَّ ارْكَعْ فَاطْمَئِنَّ ثُمَّ اسْجُدْ فَاطْمَئِنَّ سَاجِدًا ثُمَّ ارْفَعْ حَتَّى تَطْمَئِنَّ قَاعِدًا ثُمَّ اسْجُدْ حَتَّى تَطْمَئِنَّ سَاجِدًا ثُمَّ ارْفَعْ ثُمَّ افْعَلْ ذَلِكَ حَتَّى تَفْرُغَ مِنْ صَلَاتِكَ»