Malachi 3:1-3

Behold, I will send my messenger, and he shall prepare the way before me: and the Lord, whom ye seek, shall suddenly come to his temple, even the messenger of the covenant, whom ye delight in: behold, he shall come, saith the LORD of hosts. But who may abide the day of his coming? and who shall stand when he appeareth? for he is like a refiner’s fire, and like fullers’ soap: And he shall sit as a refiner and purifier of silver: and he shall purify the sons of Levi, and purge them as gold and silver, that they may offer unto the LORD an offering in righteousness.

Before the second coming of Christ, God promises us that he will send a messenger to prepare the way before him. We know this is before the second coming because it says that the Lord will come to his temple. When Christ came the first time he did not suddenly at his temple. It also states that the messenger will purify the house of Levi, the ministry. Since  Christ started the ministry, there was nothing to purify back then. This means that this must happen before the second coming of  Christ. This messenger is coming now to prepare the way. His name is the John the Baptist and he is fulfilling this prophesy.