What is the meaning of Matthew 11:13-15?

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. 15 He that hath ears to hear, let him hear. (Matthew 11:13-15 KJV)

William Burkitt’s Commentary

Here is still a farther commendation of John. The law and the prophets till the coming of John, did foretell the Messiah, but not so determinately, not so nearly, not so clearly as John did: and accordingly, he was that Elias which Isaiah and Malachi foretold should be the barbinger and forerunner of Christ. But why hath John the Baptist the name of Elias? Possibly because they were alike zealous in the work of God; they were alike successful in that work, and they were alike persecuted for their work: the one by Jezebel, the other by Herodias.