Prophets Isaiah and Malachi predicted the coming of John, just as they did that of Christ (Isaiah 40:3-5; Malachi 3:1). The angel announced John's imminent coming, as He did that of Jesus (Luke 1:13,30,31).

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8