Short answer
Tell children to pray from age seven, and be firmer from age ten, as the Prophet ﷺ instructed. In the Hanafi school the guardian is required to order prayer at seven. Prayer itself becomes fard on the child only at puberty.
It is wajib on the guardian to command a child to pray at seven. At ten the guardian may discipline lightly, by hand and not with a stick, no more than three times, never on the face. Before puberty the child's prayers count as voluntary and are rewarded.
The four schools agree on this.
Explanation
The Prophet ﷺ said: command your children to pray when they are seven, discipline them for it when they are ten, and separate their beds. The four schools agree on these two ages. The aim is that by puberty, when prayer becomes fard, the child already prays all five without being told.
Before seven: let children stand beside you, copy the movements and learn short surahs. Small children often love this. Bring them to the mosque when they will not disturb others.
From seven:
- Teach wudu and how to pray step by step.
- Start with one or two prayers a day and build up to five.
- Use praise, rewards and a salah tracker chart.
- Pray together as a family.
From ten: be firm. The permission to discipline is a last resort with strict limits, and in our time scholars stress that warmth, routine and example usually work better. Harsh punishment that makes a child hate prayer defeats the purpose. See whether hitting children is allowed.
The same ages apply to boys and girls. A child's prayer is valid even if it has mistakes, and the parent is rewarded for every prayer the child learns.
The evidence
Quran, Surah Taa-Haa 20:132
وَأْمُرْ أَهْلَكَ بِٱلصَّلَوٰةِ وَٱصْطَبِرْ عَلَيْهَا ۖ لَا نَسْـَٔلُكَ رِزْقًۭا ۖ نَّحْنُ نَرْزُقُكَ ۗ وَٱلْعَٰقِبَةُ لِلتَّقْوَىٰ ﴿١٣٢﴾
And enjoin prayer upon your family [and people] and be steadfast therein. We ask you not for provision; We provide for you, and the [best] outcome is for [those of] righteousness.
Parents are commanded to bring their family to prayer.
Quran, Surah At-Tahrim 66:6
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ قُوٓا۟ أَنفُسَكُمْ وَأَهْلِيكُمْ نَارًۭا وَقُودُهَا ٱلنَّاسُ وَٱلْحِجَارَةُ عَلَيْهَا مَلَٰٓئِكَةٌ غِلَاظٌۭ شِدَادٌۭ لَّا يَعْصُونَ ٱللَّهَ مَآ أَمَرَهُمْ وَيَفْعَلُونَ مَا يُؤْمَرُونَ ﴿٦﴾
O you who have believed, protect yourselves and your families from a Fire whose fuel is people and stones, over which are [appointed] angels, harsh and severe; they do not disobey Allah in what He commands them but do what they are commanded.
Guiding one's children is part of protecting them.
Sunan Abi Dawud 495
Graded hasan sahih... مروا أولادكم بالصلاة وهم أبناء سبع سنين ...
"Command your children to pray when they are seven years old, and discipline them for it when they are ten."
Sets the two ages.
Jami' at-Tirmidhi 407
Graded hasan sahih... علموا الصبي الصلاة ابن سبع سنين ...
"Teach the child prayer at seven years old."
The starting age is about teaching, not only ordering.
Where the ruling is recorded
- al-Durr al-Mukhtar, Kitab al-Salah, opening section. The guardian's duty at seven and the limits of discipline at ten.
- Nur al-Idah with Maraqi al-Falah, Kitab al-Salah, opening section. On commanding children to pray.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.