Isa 40:3, Mal 4:5-6, Mt 3:1-3, Mt 11:13-14
An angel said that when John the Baptist was born, he would be the preparer of the way for Christ. (Lk 1:17)
Lk 1:17 And he shall go before him in the spirit and power of Elias, to turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just; to make ready a people prepared for the Lord.
The Old Testament prophesied that someone like the prophet Elijah would come, who would prepare the way for Christ. (Isa 40:3, Mal 4:5-6)
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.
Mal 4:5 Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the Lord: 6 And he shall turn the heart of the fathers to the children, and the heart of the children to their fathers, lest I come and smite the earth with a curse.
John the Baptist is the man who will prepare the way for Christ as prophesied in the Old Testament. (Mt 3:1-3, Mt 11:13-14)
Mt 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.
Mt 11:13 For all the prophets and the law prophesied until John. 14 And if ye will receive it, this is Elias, which was for to come.