In the sixth place, Chemnits identifies the New Testament as the covenant of grace described in Jer 31:33,34. This is somewhat interesting given Chemnitze's insistence on the Lord’s Supper being a Testament earlier in the book. But here we have to realize that there are different types of covenants, one being a testament, or will. Covenant merely meaning a form of binding agreement entered into between two or more people. A testament is this, though it requires nothing of the receiving party. So Jeremiah refers to a new covenant. In the institution of the Lord’s Supper we learn exactly what type of covenant this new covenant is. It is a testament, sealed in the body and blood of our Lord Jesus Christ. Therefore it is still not permissible to translate the institution of the Lord’s Supper as a covenant, as this leads to ambiguity. It is the New Testament in the blood of Jesus Christ, whereby we children of God receive our inheritance, the forgiveness of sins.
So Chemnitz notes that it is “necessary for the salvation of individuals that they be brought into this covenant and remain in it.” No perseverance of the saints here. Chemnitz also notes that we are brought into this covenant through baptism, and are kept in it also through the word. However the New Testament is for fearful souls concerned with whether or not they are still in this covenant of grace.
This is necessary because we poor souls, sinners that we are often break with the covenant. In short we sin, and do not lead the holy lives to which we are called. Only through faith and true repentance are we brought back into this covenant. So to strengthen our faith, and to assure us that we are continually renewed into this covenant of the New Testament, though we fall, Jesus gives us His body and blood to eat and to drink. This is the blood of the New Testament, and by giving it to us, He ratifies and confirms the new covenant of grace to us. So we have no doubt that He wills to keep us in this covenant.
The problem is that it contradicts the nature of a pledge, sign or guarantee if “we are separated by an immense distance and cut off from those things which ought to strengthen us and instead receive and possess only bread and wine.” So it is necessary that we not only receive bread and wine in the New Testament, but those very things Christ says are present in the Lord’s Supper, His body and His blood.