Nathanael wants to understand how Jesus knows him before even meeting him. A legitimate question, don’t you think? Nathanael has judged Jesus before meeting Him, but this judgment is based upon where Jesus comes from, not on who Jesus is or is not. When Philip tells Nathanael he and Andrew and Peter “have found the one Moses wrote about in the Law, and about whom the prophets also wrote — Jesus of Nazareth, the son of Joseph” (John 1:45) Nathanael responds by rhetorically asking, “Can anything good come from [Nazareth]?” (John 1:46) He dismisses Jesus solely based on tradition.
Yet, when Jesus sees Nathanael from a distance, He says, “Here is a true Israelite, in whom there is nothing false.” (John 1: 47) He already knows Nathanael. Jesus tells Nathanael how He knows Him, “I saw you while you were still under the fig tree before Philip called you.” (John 1:48) Essentially Jesus tells Nathanael, “Hey, I’ve always known you.”
Because Jesus shows His omniscience briefly to Nathanael, the man believes, saying, “Rabbi, You are the Son of God; You are the King of Israel.” (John 1:49)
Jesus may as well have laughed, a joyful, not derisive laugh because here is one who believes because Jesus is able to see him under a fig tree. “I tell you,” Jesus says, “you shall see greater things than that.” (John 1:50)
“Praise be to the God and Father of our Lord Jesus Christ, who blesses us in the heavenly realms with every spiritual blessing in Christ. For He chose us in Him before the creation of the world to be holy and blameless in His sight. In love He predestined us to be adopted as His sons through Jesus Christ, in accordance with His pleasure and will — to the praise of His glorious grace, which He freely gives us in the One He loves.” (Ephesians 1:3-6)