Adam Clarke on John 1:47

Behold an Israelite indeed - A worthy descendant of the patriarch Jacob, who not only professes to believe in Israel's God, but who worships him in sincerity and truth, according to his light.

In whom is no guile! - Deceitfulness ever has been, and still is, the deeply marked characteristic of the Jewish people. To find a man, living in the midst of so much corruption, walking in uprightness before his Maker, was a subject worthy the attention of God himself. Behold this man! and, while you see and admire, imitate his conduct.