Those parents who encourage their kids to say prayers while they are not yet religiously obliged to, Allah Almighty writes the reward of the very prayers for the parents as well. On the day of resurrection, the person comes to understand that he has said about sixty years of prayers but there are some more prayers beside his prayers, he is surprised and asks: O Allah! During these sixty years, I have said my prayers only once, why are there more prayers in my record of deeds? He will be addressed: have you not encouraged your child to say prayers? All the prayers that your child has said, have been both written in his record of deeds and yours, because you guided him to do so.
source : erfan.ir