It was a commonly accepted understanding amongst Jews that God gave the law to Moses through angels.1 This understanding was most likely based on what Moses says in Deuteronomy 33:2 as well as the testimony of David in Psalm 68:17. The New Testament writers affirm this understanding to be correct (Acts 7:53; Hebrews 2:2).
19 Why then the law? It was added because of transgressions, until the offspring should come to whom the promise had been made, and it was put in place through angels by an intermediary.