The following is excerpted from "On Two Kinds of Obedience," a tract written by Michael Sattler. He was also the author of the Schleitheim Confession, which was originally printed under the title, "Brotherly Agreement of Some Children of God." This confession is generally recognized as the first confession of those who were called "Anabaptists" by their persecutors.
Obedience is of two kinds, servile and filial. The filial has its source in the love of the Father, even though no other reward should follow, yea even if the Father should wish to damn His child; the servile has its source in a love of reward or of oneself. The filial ever does as much as possible, apart from any command; the servile does as little as possible, yea nothing except by command. The filial is never able to do enough for Him; but he who renders servile obedience thinks he is constantly doing too much for Him.