Adam Clarke on Matthew 11:14

This is Elias, which was for to come - This should always be written Elijah, that as strict a conformity as possible might be kept up between the names in the Old Testament and the New. The Prophet Malachi, who predicted the coming of the Baptist in the spirit and power of Elijah, gave the three following distinct characteristics of him. First, That he should be the forerunner and messenger of the Messiah: Behold I send my messenger before me, Mal 3:1. Secondly, That he should appear before the destruction of the second temple: Even the Lord whom ye seek shall suddenly come to his temple, ibid. Thirdly, That he should preach repentance to the Jews; and that, some time after, the great and terrible day of the Lord should come, and the Jewish land be smitten with a curse, Mal 4:5, Mal 4:6. Now these three characters agree perfectly with the conduct of the Baptist, and what shortly followed his preaching, and have not been found in any one else; which is a convincing proof that Jesus was the promised Messiah.