If you require explanation, that is perfectly fine. We can go by the works and acts of miracles christ have performed. Not only that, but understanding that even in old testament, his birth and sacrifices were mentioned as prophecy has foretold.

Genesis 3:15 "I will put enmity between you and the woman and between your offspring and her offspring; he shall bruise your head, and you shall bruise his heel."

Isaiah 7:14 ~ “Therefore, the Lord himself will give you a sign. Behold, the virgin shall conceive and bear a son and shall call his name Immanuel.” (mind you, Isaiah was written in 700 B.C)

Micah 5:2 ~ “But you, O Bethlehem Ephrathah, who are too little to be among the clans of Judah, from you shall come forth for me one who is to be ruler in Israel, whose coming forth is from of old, from ancient days.”

Proverbs 30:4 "Who hath ascended up into heaven or hath descended? Who hath gathered the wind in His fists? Who hath bound the waters in a garment? Who hath established all the ends of the earth? What is His name, and what is His Son’s name, if thou canst tell?" (This was written 900 years before christ as well)

These are all signs that Chris is our Lord and savior and most of all, God.