Luke 1:70

As he spake by the mouth of his holy prophets, which have been since the world began:

The verse belongs to the account of Zacharias ministering in the temple at the announcement of John's birth, before the golden altar in the holy place of the sanctuary while the cloud of incense with the prayers of Israel ascended before God. An angel stood on the right side of the altar, a position indicating favor, sent from heaven to announce that Zacharias's many years of prayer for the coming of the Redeemer were about to be answered, though the mercy seemed too great to credit and left him filled with fear and self-condemnation. It is part of the account of the promised son who would go before the Lord to prepare His ways, belonging to the story of the forerunner of Christ whose coming was awaited by faithful people in Israel. It belongs to Zacharias's prophecy after John's birth, when filled with the Holy Spirit he prophesied and thereby became part of the continuing prophetic witness through whom God had spoken through the ages.

God spoke by the mouth of His holy prophets from the beginning, from the earliest times and throughout the ages in a long line of prophetic witness concerning the coming Savior. Those words were inspired by the Holy Spirit, and the voice of Christ spoke through the prophets and patriarchs. They foretold Christ's life, mission, suffering, death, and resurrection and testified to God's redemption of His people through the promised Savior from David's line. They were fulfilled in Jesus and provide clear evidence of Christ's identity and of the events that happened to Him.

The verse places God's promised mercy and redemption within that prophetic message, including the covenant oath to Abraham and a deliverance that enables God's people to serve Him without fear, in holiness and righteousness throughout their lives. The passage presents Christ as the Instructor who brings light to people in spiritual darkness and as the Dayspring, the dawn of hope. Zacharias's prophecy connects those earlier promises with God's coming to redeem His people, identifying his child as the Messiah's herald appointed as a prophet to prepare the way for the Lord and announcing that the promised Messiah's advent was near. John was appointed to prepare the way, but the people rejected his message and were thereby prepared to reject Christ as well.

The Old and New Testament Scriptures are in harmony, and careful study and comparison of passages on the same subject brings clarity to texts that first seem dark. In ancient times God spoke to men by the mouth of prophets and apostles, which stands in contrast to the present, for in these days He speaks to them by the Testimonies of His Spirit. There was never a time when God instructed His people more earnestly concerning His will and the course He would have them pursue than He instructs them now.