Matthew 13:37

"And He answered," so it is said, "and said unto them, He that soweth the good seed is the Son of Man; the field is the world, the good seed, these are the children of the kingdom, but the tares are the children of the wicked one; the enemy that soweth them is the devil; and the harvest is the end of the world, and the reapers are angels. As therefore the tares are gathered and burned in the fire; so shall it be in the end of this world. The Son of Man shall send His angels, and they shall gather out of His kingdom all things that offend, and them which do iniquity; and shall cast them into the furnace of fire, there shall be weeping and gnashing of teeth. Then shall the righteous shine forth as the sun in the kingdom of their Father." For whereas He Himself is the sower, and that of His own field, and out of His own kingdom He gathers, it is quite clear that the present world also is His. But mark His unspeakable love to man, and His leaning to bounty, and His disinclination to punishment; in that, when He sows, He sows in His own person, but when He punishes, it is by others, that is, by the angels.

The Lord styles Himself the Son of Man, that in that title He might set an example of humility; or perhaps because it was to come to pass that certain heretics would deny Him to be really man; or that through belief in His Humanity we might ascend to knowledge of His Divinity.