John Chrysostom
Hastening to Nathanael, Philip says to him, "We have found Him of whom Moses in the Law and the Prophets wrote." Do you see what an anxious soul he had? Do you see how often he pondered what Moses had written, and how he awaited the coming of Christ?
The word "found" shows men who are constantly seeking. He says this to give credibility to his preaching by appealing to Moses and the Prophets, and thereby to move his hearer to attention.
Nathanael was a precise man and sought out the truth in everything, as Christ Himself testified and as the event showed. Therefore Philip did well to refer him to Moses and the Prophets. In this way he disposed Nathanael to receive Him whom he preached to him.
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If Philip calls Christ the son of Joseph, do not be troubled. At that time He was still considered the son of Joseph.
But how is it clear to you, Philip, that He is the very One of whom Moses and the Prophets wrote? What proof will you give us? Verbal testimony alone is not enough. What sign did you see? What miracle? In such matters it is not safe simply to believe without proofs.
What proof, then, do you have? Philip answers us: the same as Andrew had. Andrew lacked the power to describe the wealth he had found. Finding no words to describe this treasure, he led his brother to Him whom he had found.
So also Philip does not explain to Nathanael why Jesus is the Christ, or how the prophets foretold Him. Instead, he draws him to Jesus, knowing that he will not depart from Jesus once he tastes His words and His teaching.