A voice of one calling: In Malachi 3:1, this person (possibly the Elijah of Malachi 4:5) was God's messenger who prepared the way for God's coming. In the Gospels, people identified this announcer as John the Baptist (Matthew 3:3; Mark 1:3; Luke 3:4; John 1:23).
Prepare the way … make a straight highway: The announcer's message would speed up God's coming (see Isaiah 35:8). As God made a way for Israel through the Red Sea (Isaiah 43:16), a way would also be opened for the Lord (see 52:11–12).