If people do not receive God's inheritance through the law, why was the law given to Moses? It was to show people their sins and make it clear that sinful actions are wrongs done against God. People cannot rely on their own goodness to save them. Instead, they must trust in God (see Romans 3:19–20; 4:15; 5:20; 7:7–13).
until the arrival of the seed to whom the promise referred: See Galatians 3:16. While the promise is permanent, the law of Moses was temporary. With Christ’s coming, the law was fulfilled (see Matthew 5:17–20; compare Matthew 3:13–15; John 19:30). God's acceptance is based entirely on faith in Christ.
through angels: Deuteronomy 33:2 in the Greek version (the Septuagint) describes the Lord's coming from Sinai “with myriads of holy ones, angels with him at his right hand.” See also Psalm 68:17; Acts 7:38, 53; Hebrews 2:2.
By a mediator: The mediator was Moses (see Exodus 20:19; Deuteronomy 5:24–27). As a mediator, Moses spoke to God for the people and spoke to the people for God.