Priest is not in the Greek but must be repeated from verse 15. Because of the last clause of verse 16, namely, through the power of a life which has no end, it may be best to translate He was made a priest as “He became a priest.” Otherwise one might wrongly assume that the passive expression would be better rendered as “God made him a priest.”
There is some doubt about the exact meaning of the phrase which Revised Standard Version translates “not according to a legal requirement concerning bodily descent,” and Good News Translation not by human rules and regulations. The literal translation is “according to a law of a fleshly command.” There are several aspects of the problem. (1) “Law” may also mean “principle,” as in Romans 7.23, but this is not its meaning in the rest of Hebrews 7. (2) What is the relation between “law” and “command”? The most likely meaning seems to be “according to the legal force of a fleshly command”; that is, the individual command is backed by the force of the Law as a whole. (3) “Fleshly” may mean (a) generally “human,” (b) “outward,” “earthly,” or (c) “to do with bodily descent.” Bijbel in Gewone Taal and other common language translations agree with Good News Translation in choosing meaning (a), but the writer would probably not have described the Old Testament Law as “human” in this negative sense. (b) is reflected in Moffatt “external,” Knox “outward,” Phillips “a command imposed from outside,” New English Bible “earth-bound,” and Translator’s New Testament “earthly.” (c) is reflected in Biblia Dios Habla Hoy which has simply “a law which says from which family he must come,” New American Bible “a commandment concerning physical descent,” and Barclay “any regulation based on the rule of physical descent” (compare Traduction œcuménique de la Bible). Meaning (c) seems to fit in best with the earlier emphasis in chapter 7 on Abraham’s and Levi’s descendants, and on Melchizedek’s lack of them.
The phrase not by human rules and regulations may be rendered as “he did not become a priest because of rules and regulations about being descended from a particular person” or “… rules and regulations about the family to which he belonged.”
Finally, the expression but through the power of a life which has no end may be rendered as “but he did become a priest because of the power of his life which will never end” or “… which goes on forever.”
The most probable meaning of the verse, therefore, is “He has been made a priest, not by the legal power of a rule which said from which family he must come, but by the power of a life which cannot be destroyed,” or even “… which nothing can destroy.”
Quoted with permission from Ellingworth, Paul and Nida, Eugene A. A Handbook on The Letter of the Hebrews. (UBS Handbook Series). New York: UBS, 1983. For this and other handbooks for translators see here .