The child did a good deed for me by washing clothes.

Parents must be very moved when children do things for their parents, which proves that children have grown up. You can express your feelings like this:

Baby, when mom came home to wash clothes today, she found that the clothes had been washed. When I asked, it turned out that you washed it for me. My mother was in tears at that time. You just turned 10 this year, but you already know how to help your mother share the housework. She was deeply moved by your understanding and gratified by your filial piety. It seems as if you were born yesterday. In a blink of an eye, you have grown into a big boy and know how to help your mother. Mom is very happy and happy. It is our destiny to be your mother. Mom loves you very much, and I hope you will be a sensible and responsible man in the future!