Children sometimes do foolish things. Even after bar mitzvah, it is not uncommon for immaturity to play a role in one’s choices in life.
One young non-Jew wanted many things that his parents refused to give him. He found a solution for his lack of funds: he began to shoplift from local merchants. He was very good at this and was never caught. Eventually, he understood that stealing is wrong and changed his ways, but he never returned what he had appropriated in his youth.
When he grew older, he began to notice a deep-rooted longing for something in the depths of his soul, but he could not figure out what he lacked. After much searching, he began to explore Yiddishkeit and found that it resonated in his soul. When he learned Torah, he felt like he was home. In his heart, he felt that he should convert and did so. But he wondered about all the goods he had taken as a non-Jew. Of course, a ger is compared to a newborn baby, as we find on Yevamos 22. Nevertheless, he found it difficult to understand why he was not obligated to repay what he had stolen as a non-Jew.
When this question was presented to the Chavos Ya’ir, he ruled that the goods must be returned. “Although the rule is that a convert is like a newborn baby, there are exceptions to this rule. If a non-Jew borrowed money or stole goods and then converted, he must still repay the loan or return the stolen goods. This is clear, since even as a non-Jew he was obligated to return the stolen goods or repay the loan. Becoming a Jew does not forgive one’s debts from when he was a non-Jew and returning stolen objects are no different” (Shu”t Chavos Ya’ir #79).