“They shall build up [Isaiah 61:4], that is, not for themselves, but to be of service to others also. All this we had earlier. He is saying that Christians are not only such as praise God, but they will also produce others and be concerned about their enlightenment and conversion. These are the two tasks of the Christians, to glorify God and to convert others. He who converts an ungodly man brings the best sacrifice, not offering an ox but a living sacrifice. This is the sum of the prophets, to attribute to the Christian these two sacrifices: to praise God and to convert sinners, instead of all the endless ceremonies of the Law” (LW 17:336).