Why do some reformed churches practice confirmation at a certain age? This seems to suggest that certain age and depth of theology is necessary in order to be a full member of the covenant community. But if an adult converts we do not ask him to be catechized for a year do we? Yet around age 13 some denominations have a "confirmation class" for around a year so that the catechumen can get his doctrine straight prior to communion. I don't get it. Where biblically does this come from?