What was the rite of passage called when a son was ready to work with his father?

Les explains that when a father agreed the young man was ready to come in with him in his business, the son went through a rite of passage called adoption. This was not adoption as taking a child from another union and legally bringing them in. The Scripture word meant being placed as a full operating son of the father, on equal basis with him in responsibility, function, and everything else. Paul uses this term as a schoolmaster. The servant had been hired and instructed to bring the child to the place where he could step right in and work with the father. Les says the Law was intended to do that for Israel, preparing them so when Messiah came they were ready, and it carries into the Gentile economy, with the Law given to prepare everything for Messiah to fulfill the work of the Cross.