Malachi 4:5

But since the Savior was the beginning of the resurrection of all people, it was fitting that the Lord alone should rise from the dead, by whom too the judgment is to enter the whole world, that they who have wrestled worthily may be also crowned worthily by him, by the illustrious Arbiter. [That is, he] himself first accomplished the course, and was received into the heavens, and was set down on the right hand of God the Father, and is to be manifested again at the end of the world as judge. It is a matter of course that his forerunners must appear first, as he says by Malachi and the angel, "I will send to you Elijah the Tishbite before the Day of the Lord, the great and notable day, comes; and he shall turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just, lest I come and smite the earth utterly." These, then, shall come and proclaim the manifestation of Christ that is to be from heaven; and they shall also perform signs and wonders; in order that people may be put to shame and turned to repentance for their surpassing wickedness and impiety.

"And I saw another angel ascending from the east, having the seal of the living God" He speaks of Elias the prophet, who is the precursor of the times of Antichrist, for the restoration and establishment of the churches from the great and intolerable persecution. We read that these things are predicted in the opening of the Old and New Testament; for He says by Malachi: "Lo, I will send to you Elias the Tishbite, to turn the hearts of the fathers to the children, according to the time of calling, to recall the Jews to the faith of the people that succeed them." And to that end He shows, as we have said, that the number of those that shall believe, of the Jews and of the nations, is a great multitude which no man was able to number. Moreover, we read in the Gospel that the prayers of the Church are sent from heaven by an angel, and that they are received against wrath, and that the kingdom of Antichrist is cast out and extinguished by holy angels; for He says: "Pray that ye enter not into temptation: for there shall be a great affliction, such as has not been from the beginning of the world; and except the Lord had shortened those days, no flesh should be saved." Therefore He shall send these seven great archangels to smite the kingdom of Antichrist; for He Himself also thus said: "Then the Son of man shall send His messengers; and they shall gather together His elect from the four corners of the wind, from the one end of heaven even to the other end thereof." For, moreover, He previously says by the prophet: "Then shall there be peace for our land, when there shall arise in it seven shepherds and eight attacks of men; and they shall encircle Assur," that is, Antichrist, "in the trench of Nimrod," that is, in the nation of the devil, by the spirit of the Church. Similarly when the keepers of the house shall be moved. […]

Who of those who hear Jesus say of John, "If you wish to receive it, he is Elijah who is to come," would not inquire how John says to those who ask, "Are you Elijah?" "I am not"? Will he not also inquire how one ought to consider John himself to be Elijah who is to come, according to Malachi's statement: … "And behold, I am sending you Elijah the Tishbite before the great and renewed Day of the Lord comes, who will restore the heart of the father to his son and the heart of a man to his neighbor, lest I come and smite the earth utterly"?

And what is the source of your belief that Elijah who is to come will baptize? He did not even baptize the wood on the altar in the times of Ahab, when it needed a bath that it might be burned up when the Lord appeared in the fire. He commanded the priests to do this, and not only once, for he says, "Do it a second time, when also they did it for a second time." And "Do it a third time, when also they did it a third time." How, then, will he who did not baptize at that time but gave the task to others, baptize when he has come in fulfillment of things said by Malachi? Christ therefore does not baptize in water but his disciples. He reserves for himself the act of baptizing with the Holy Spirit and fire.

I fully expect these heretics to seize upon the example of Elijah as reincarnated in John the Baptist, and thus they would have become our Lord espousing the doctrine of reincarnation. "Elijah indeed has come, and they knew him not." And again, "And if you are willing to receive it, here is Elijah who was to come." Was the question of the Jews to John, "Are you Elijah?" to be understood in a Pythagorean sense and not in reference to the divine pronouncement: "Behold, I send you Elijah, the Tishbite"? But their theory of transmigration refers to the recall of a soul that had died long before and to its insertion in some other body. Elijah, however, is to return not after leaving this life by death, not to be returned to his body, since he never left it, but he will come back to the world from which he has been removed. He will return not to take up a life he had left off but for the fulfillment of a prophecy. He will come back as Elijah, with the same name. How, then, could John be Elijah? The voice of the angel tells us: "And he shall go before the people in the spirit and power of Elijah," not in the soul or body of Elijah. These substances are the specific property of each man, while "spirit and power" are extrinsic gifts conferred by the grace of God, and so they may be transferred to another according to the will of God as happened long ago with respect to the spirit of Moses.