Accrue a Crew

On the day of his Bar Mitzvah, a boy receives the title bachur. What is the idea behind this?

This is because from that moment of his Bar Mitzvah onward, he is granted true free will (bechirah). Until then, he is considered a katan and does not yet possess a yetzer tov.

Another explanation is that the term bachur is related to bachar—“chosen”—signifying that upon reaching Bar Mitzvah, he becomes a more integral part of the chosen nation.