The Prophet ﷺ said: Command a boy to pray when he reaches the age of seven years. When he becomes ten years old, then beat him for prayer.  

قَالَ النَّبِيُّ ﷺ مُرُوا الصَّبِيَّ بِالصَّلاَةِ إِذَا بَلَغَ سَبْعَ سِنِينَ وَإِذَا بَلَغَ عَشْرَ سِنِينَ فَاضْرِبُوهُ عَلَيْهَا  

The Messenger of Allah ﷺ said: Command your children to pray when they become seven years old, and beat them for it (prayer) when they become ten years old; and arrange their beds (to sleep) separately.  

قَالَ رَسُولُ اللَّهِ ﷺ مُرُوا أَوْلاَدَكُمْ بِالصَّلاَةِ وَهُمْ أَبْنَاءُ سَبْعِ سِنِينَ وَاضْرِبُوهُمْ عَلَيْهَا وَهُمْ أَبْنَاءُ عَشْرِ سِنِينَ وَفَرِّقُوا بَيْنَهُمْ فِي الْمَضَاجِعِ  

Waki' misunderstood the name of Dawud b. Sawar. Abu Dawud al-Tayalisi has narrated this tradition from him. He said: Anu Hamzah Sawar al-Sairafi.  

Hisham ibn Sa'd reported: We entered upon Mu'adh ibn Abdullah ibn Khubayb al-Juhani. He said to his wife: When (at what age) should a boy pray? She replied: Some person of us reported: The Messenger of Allah ﷺ was asked about it; he said: When a boy distinguishes right hand from the left hand, then command him to pray.  

عَنْ رَسُولِ اللَّهِ ﷺ أَنَّهُ سُئِلَ عَنْ ذَلِكَ فَقَالَ إِذَا عَرَفَ يَمِينَهُ مِنْ شِمَالِهِ فَمُرُوهُ بِالصَّلاَةِ