What is the religious ruling on touching dogs in childhood out of ignorance, and how is the resulting impurity purified?

The first thing one must safeguard are the obligatory duties (Fara'id), then to increase in supererogatory acts (Nawafil) and acts of obedience (Ta'at), and to abstain from all sins and forbidden acts. What was committed before puberty carries no sin, as the pen is lifted from the child. As for what occurred after puberty, one must repent from it, regret it, and not return to it. Touching dogs and playing with them in childhood is not blameworthy, because their saliva does not remain on the body, and their fur is pure, according to the preponderant opinion.