Lk 3:3-6, Mt 3:1-3, Mk 1:1-4, Lk 1:76-77, Jn 1:22-23

In the Old Testament, Isaiah prophesied that the voice of a crying man would prepare the way for God. (Isa 40:3-5)

Isa 40:3 The voice of him that crieth in the wilderness, Prepare ye the way of the Lord, make straight in the desert a highway for our God. 4 Every valley shall be exalted, and every mountain and hill shall be made low: and the crooked shall be made straight, and the rough places plain: 5 And the glory of the Lord shall be revealed, and all flesh shall see it together: for the mouth of the Lord hath spoken it.

John the Baptist is the voice of a cryer who prepared the way for Christ, as prophesied by Isaiah in the Old Testament. (Luke 3:3-6, Matthew 3:1-3, Mark 1:1-4, Luke 1:76-77, John 1:22-23)

Luke 3:3 And he came into all the country about Jordan, preaching the baptism of repentance for the remission of sins; 4 As it is written in the book of the words of Esaias the prophet, saying, The voice of one crying in the wilderness, Prepare ye the way of the Lord, make his paths straight. 5 Every valley shall be filled, and every mountain and hill shall be brought low; and the crooked shall be made straight, and the rough ways shall be made smooth; 6 And all flesh shall see the salvation of God.

Matthew 3:1 In those days came John the Baptist, preaching in the wilderness of Judaea, 2 And saying, Repent ye: for the kingdom of heaven is at hand. 3 For this is he that was spoken of by the prophet Esaias, saying, The voice of one crying in the wilderness, Prepare ye the way of the Lord, make his paths straight.

Mark 1:1 The beginning of the gospel of Jesus Christ, the Son of God; 2 As it is written in the prophets, Behold, I send my messenger before thy face, which shall prepare thy way before thee. 3 The voice of one crying in the wilderness, Prepare ye the way of the Lord, make his paths straight. 4 John did baptize in the wilderness, and preach the baptism of repentance for the remission of sins.

Luke 1:76 And thou, child, shalt be called the prophet of the Highest: for thou shalt go before the face of the Lord to prepare his ways; 77 To give knowledge of salvation unto his people by the remission of their sins,

John 1:22 Then said they unto him, Who art thou? that we may give an answer to them that sent us. What sayest thou of thyself? 23 He said, I am the voice of one crying in the wilderness, Make straight the way of the Lord, as said the prophet Esaias.