Luke 1:64

And his mouth was opened immediately, and his tongue loosed, and he spake, and praised God.

The loosening of the tongue concludes what began when Zacharias stood 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 as an indication of favor to announce that his prayers of many years for the coming of the Redeemer were about to be answered. The mercy seemed too great to credit, and left him filled with fear and self-condemnation. He lost the power of speech because he did not believe the angel's words, being struck dumb for his unbelief. When the angel's prediction and promise about John was fulfilled at John's birth, his mouth was opened immediately and his tongue was loosed, his speech was restored and he praised God.

His restored speech marked the fulfillment of the angel's prediction about a son who would prepare a people for the Lord. After his speech was restored Zacharias was filled with the Holy Spirit and prophesied. The restoration was a miraculous, remarkable sign of God's power connected with the circumstances of John's birth and God's work through him. It attested the forerunner's birth and mission. It astonished the people and drew awe and attention across the hill country of Judea where people wondered what kind of child John would be, and its importance was remembered when John later appeared as a prophet.

The events surrounding the restored speech pointed people toward the coming Messiah whose way John was to prepare, preparing a people for the Lord and for Christ's coming. The same loosening of the tongue to praise God is echoed in a later experience in which one who had doubted God's power was struck unable to speak. Then the next morning the tongue was loosed, speech and voice were regained, and praise was joyfully given and shouted to God. That later account includes that of a woman who, after being unable to speak, regained her voice the next morning and joyfully praised God.