Amr bin Shu'ayb narrates from his father, and he from his grandfather, that the Messenger of Allah (peace and blessings be upon him) said: "Teach children to pray at the age of seven, punish them for not praying at the age of ten, and separate their beds. And when you marry your slave-girl to your slave or servant, then never look at his awrah; and the awrah is the area between the navel and the knee."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3236