Sayyiduna Anas (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "Command them to pray at the age of seven, and beat them for the prayer at the age of thirteen!"
Al-Tabarani recorded it; its narration contains Dawud bin al-Muhabbar, whom Ahmad, al-Bukhari (may Allah have mercy on him) and a group declared da'if (weak), while Yahya bin Ma'in declared him thiqah (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1629