Luke 1:73

The oath which he sware to our father Abraham,

The words belong to the prophecy uttered by Zacharias after the revelation given to him in the temple, when he was full of the Holy Ghost. That prophecy pointed to his child John as the Messiah's herald. It presented Christ's coming into the world in the gracious character of Instructor of those lying in gross darkness, viewing Him as the Dayspring in order to call forth the highest exaltation of Christ.

The oath is the promise recorded in Genesis 22, in which God swore to bless and multiply Abraham's descendants, to give them victory over their enemies, and to bless all nations through his seed. It is a promise to deliver His people from enemies so that they may serve Him without fear in holiness and righteousness before Him all the days of life. God fulfills these promises for His own glory and for His people's good.

The oath is remembered in God's holy covenant, and its fulfillment is bound up with the coming Redeemer and the Messiah's kingdom. At John's birth it was the great object of hope as deliverance of Israel out of the hand of enemies, looked for as national foes, by the coming of a King in righteousness and the establishment of Israel as a holy nation, though the nature of the Messiah's kingdom was not fully understood. The announcement to Zacharias that his long-standing prayers for the Redeemer were about to be answered shows the oath was being fulfilled in the birth and mission of John.

The prophecy presents God as visiting and redeeming His people and points to John as sent ahead of the Lord to prepare the way for Christ. It describes Christ's advent as the coming of the Dayspring as Instructor of those in gross darkness, meant to call forth the highest exaltation of Christ. Zacharias should have remembered the oath's promised fulfillment when he doubted the angel's message about John's birth, for Abraham and Sarah had already shown that God fulfills His promise despite old age, proving that nothing is impossible with God. After thirty years of tumult and change in which the prophecy had been largely lost sight of, it was called back to mind by the excitement over John's ministry. Rejection of John's warning hardened the people against Christ, who came to save them but was rejected.