Note: I preached Sunday from Galatians 3:15-22, which meant attempting an interpretation of a notorious textus difficilis. Here are some notes:
"Now a mediator is not a mediator of one, but God is one" (Galatians 3:20).
Paul’s comment in v. 20 is notoriously difficult to interpret. The Puritan expositor Mathew Poole noted: “This is a text acknowledged by all interpreters to be very obscure. “ John Brown in 1853 observed: “Perhaps no passage in Scripture has received so many interpretations as this” (Galatians, p. 155). He then cites a scholar of his day who traced no less than 250 different interpretations of this verse! The Dutch scholar Hermann Ridderbos in 1953 said there are at least 430 interpretations of this verse (matching the 430 years of v. 17) (Galatians, p. 139).
Some immediate questions might be posed: Is the mediator here Moses, or angels (v. 19), or Christ, or any mediator? Is Paul making a positive, approving statement here, or is he quoting something his opponents have been saying? Is he contrasting the promise to Abraham and the giving of the law through Moses?
Luther interpreted the verse as follows: “God offendeth no man, and therefore needeth no mediator; but we offend God, and therefore we need a mediator” (as cited in Brown, p. 156).
If we are to attempt an interpretation we should look to the opening section of the verse: “Now a mediator is not a mediator one....” This seems to be simply making the obvious point that if there is a mediator he must be mediating between two conflicting or opposing parties. Paul then adds: “but God is one.” This seems to point to the fact that there is no inherent self-contradiction in God. He does not have self-contradictory motives. He does not act inconsistently. The larger point: God did not enter into covenant with Abraham and justify him by faith, then later decide that he had a better idea and gave the law through Moses so that men could be justified by law keeping. The giving of the law, then, does not contradict the unconditional covenant of faith that God made with Abraham.
This interpretation is supported by the next question in v. 21: “Is the law then against the promises of God?” Does the giving of the law contradict the promise given to Abraham (in Genesis 22:18)? Paul’s answer: God forbid! Me genoito! Let not such a thing be even imagined or uttered aloud!