This sermon is designed and undertaken that it might be an instruction for children and the simple-minded, what every Christian must needs know, so that he who does not know this could not be numbered with the Christians nor be admitted to any Sacrament, just as a mechanic who does not understand the rules and customs of his trade is expelled and considered incapable. Therefore we must have the young learn the parts which belong to the Catechism or instruction for children well and fluently and diligently exercise themselves in them and keep them occupied with them. Therefore it is the duty of every father of a family to question and examine his children and servants to ascertain what they know of it, or are learning and, if they do not know it, to keep them faithfully at it | The Large Catechism by Martin Luther, Paperback | Indigo Chapters