Is there a sin on someone who stole when he was eight years old that he must atone for, now that he is seventeen, and what should he do?

If a boy steals, there is no hadd (prescribed punishment) upon him, nor is he sinful, because the Prophet, peace and blessings be upon him, said: "The pen has been lifted from three, and among them is the boy until he reaches puberty." However, when he reaches puberty, he must return the money he took or destroyed to its owners, because the guarantee for damaged goods does not stipulate accountability ( taklif ). Therefore, he must return what he took or seek forgiveness.