John 1:47 - Matthew Poole's English Annotations on the Holy Bible

They are not all Israel, which are of Israel, Romans 9:6. For he is not a Jew, which is one outwardly; neither is that circumcision, which is outward in the flesh: but he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, Romans 2:28,29. Christ seeing Nathanael (though he was prejudiced by Philip's mistake, or the common mistake of his nation) coming to see him, and seeing not only his body and bodily motion, but his heart also, and the motions of that, saith of him, Behold one who is not only born an Israelite, but is a true Israelite, like his father Jacob, a plain man, Genesis 25:27; in whom is no guile; in whom there is no deceit, no doubleness of heart. Such ought Christians to be, no crafty, deceitful, double minded men, but men of great sincerity and plainness of heart, laying aside all malice, and all guile, 1 Peter 2:1, like little children, Matthew 18:3.