Romans 4:13

Heir of the world. This exact expression does not occur in any of the promises made to Abraham. It is possible that Paul is summing up all the promises in this comprehensive expression, or he may be referring particularly to the most inclusive of all the promises, “In thy seed shall all the nations of the earth be blessed” (Gen. 22:18). This was “the blessing of Abraham” that was to be extended also to the Gentiles through Jesus Christ (Gal. 3:14). All who are Christ’s are “Abraham’s seed, and heirs according to the promise” (Gal. 3:29). Since the kingdom of Christ will fill the whole earth, Abraham and his seed are indeed heirs of the world. The promise will be literally fulfilled when the kingdoms of this world are given to the people of the Most High, and Christ will reign with His saints forever and ever (Dan. 7:27).

Through the law. Literally, “through law.” There is no article in the Greek (see on ch. 2:12). Furthermore, in the Greek this phrase comes at the beginning of the verse, perhaps for emphasis: “For not through law was the promise to Abraham,” etc. Paul’s argument here closely resembles that in Gal. 3:18. There “law,” without the article (see on Rom. 2:12), is spoken of as a principle opposed to “promise.” The inheritance cannot be dependent on law, because God has granted it to Abraham by promise. Here in ch. 4:13, “law” and “righteousness of faith,” both without the article, are the two contrasting principles. Paul is asserting that the promise is to be realized and appropriated “not through law” (cf. vs. 14, 15) but “through righteousness of faith” (cf. vs. 16, 17).