Hazrat Moulana Ashraf Ali Thanwi (rahmatullahi ‘alaih) once mentioned:
Most people are not particular about giving their children an Islamic upbringing. Such people generally say, “The children are still small.” However, it should be remembered that the good values instilled in childhood are firmly embedded in the child and remain with him throughout his life. In fact, childhood is the actual period wherein the character of a child and his understanding can be correctly moulded. (Malfoozaat Hakeemul Ummat 23/219)
Source: Ihyaauddeen.co.za