What is a covenant? In English the word usually means an “agreement” or “a written contract.” But what did the word mean in Greek—specifically in the original Greek New Testament?
When Paul and others wrote about God’s covenant with man, there were two Greek words from which to choose: syntheke (soon THAY kay) and diatheke (dee ah THAY kay). As you can see, both words are built on the same stem. The first word meant “something that is arranged jointly.” It was the word used when two equal parties hammered out an agreement. Both parties expected to get their fair share from the deal. The second word meant “something arranged according to one’s own wishes.” It was the word used when one party set the terms for disposing of his property when he gave it to another.
This second word, diatheke, was always the word they used for making a legal will. The one who makes the will has complete authority over the disposition of his property. He can give it to whomever he pleases; he can establish whatever terms he wants. The one who makes the “arrangement” has total power; the one who receives the “arrangement” may accept it or reject it, but he cannot alter it.
Luke 22 provides a good example of each word. The verb form of syntheke is used when Judas and the priests discussed how he might betray Jesus and they “agreed” to give him money (v. 6). They were delighted, Judas consented, and they had a deal. Later in the chapter the verb form of diatheke appears, translated as the word “confer.” To the apostles whom he had chosen, Jesus said, “I confer on you a kingdom, just as my Father conferred one on me” (v. 29).
One word is a reciprocal agreement: “Let’s make a deal!” The other word is a one-way grant: “This is the way it is—take it or leave it!” Every time God's covenant with man is mentioned in the New Testament it is this second word. In his own authority the Father made the diatheke possible and set the terms. In humble gratitude we submit and accept.