There are two kinds of sacrifices, one earns favor and the other expresses praise and thanksgiving. Since our Lord's sacrifice on the cross we have God's forgiveness and favor. The preaching of the gospel of God's forgiveness results in changed hearts and lives that receive the Lord's Supper and do acts of mercy as sacrifices of praise and thanksgiving for what God has done for us.
We include the preaching of the Word among the sacrifices of praise of God. The reception of the Lord's Supper can be praise or thanksgiving. But it does not justify by the outward act, neither is it to be applied to others to merit the forgiveness of sins for them. Later we will explain how even a ceremony is a sacrifice. Malachi speaks about all the services of the New Testament, and not only about the Lord's Supper. Likewise, since he does not favor the pharisaic opinion of the outward act, he is not against us, but rather helps us. He requires services of the heart, through which the name of the Lord becomes truly great.
Another passage also is cited from Malachi, "He will purify the sons of Levi and refine them like gold and silver, and they will bring offerings in righteousness" (3:3). This passage clearly requires the sacrifices of the righteous, and so does not favor the opinion that the outward act [earns merit]. But the sacrifices of the sons of Levi, that is, of those teaching in the New Testament, are the preaching of the Gospel and the good fruit of preaching. About this Paul says, "To be a minister of Christ Jesus to the Gentiles in the priestly service of the gospel of God, so that the offering of the Gentiles may be acceptable, sanctified by the Holy Spirit" (Romans 15:16). He means that the Gentiles may be offerings acceptable to God through faith. (paragraphs 33-34)
Condensed from CONCORDIA: THE LUTHERAN CONFESSIONS, copyright 2005,2006 by Concordia Publishing House. Used by permission. All rights reserved. To purchase a copy of CONCORDIA, call 800-325-3040.