Diatheke, was the word chosen by the Septuagint translators to render the Hebrew berith, and it appears thus nearly 300 times in the Greek Old Testament in the sense of covenant, while suntheke and entolai are each used once only. The choice of this word seems to have been occasioned by a recognition that the covenant which God makes with men is not fully mutual as would be implied in suntheke, the Greek word commonly used for covenant (although not a New Testament word), while at the same time the rarity of wills among the Jews made the common sense of diatheke relatively unfamiliar. The Apocryphal writers also frequently use the same word in the same sense and no other.

In the New Testament diatheke is used some thirty times in a way which makes it plain that its translation must be "covenant." In Ga 3:15 and Heb 9:15-17 it is held by many that the sense of covenant must be set aside in favor of will or testament. But in the former passage it can be taken in the sense of a disposition of affairs or arrangement made by God, a conception in substantial harmony with its regular New Testament use and with the sense of berith. In the passage in Hebrews the interpretation is more difficult, but as it is acknowledged on all hands that the passage loses all argumentative force if the meaning testament is accepted, it seems best to retain the meaning covenant if possible. To do this it is only necessary to hold that the death spoken of is the death of the animal sometimes, if not, indeed, commonly slain in connection with the making of a covenant, and that in the mind of the author this death symbolized the death of the contracting parties so far at least as to pledge them that thereafter in the matter involved they would no more change their minds than can the dead. If this view is taken, this passage falls in line with the otherwise invariable use of the word diatheke by Jewish Hellenists.