Augustine of Hippo
Catena Aurea · Johannesevangelium 1
Jesus saw Nathanael coming to him, and saith of him, Behold an Israelite indeed, in whom is no guile! Nathanael saith unto him, Whence knowest thou me? Jesus answered and said unto him, Before that Philip called thee, when thou wast under the fig tree, I saw thee. Nathanael answered and saith unto him, Rabbi, thou art the Son of God; thou art the King of Israel. Jesus answered and said unto him, Because I said unto thee, I saw thee under the fig tree, believest thou? thou shalt see greater things than these. And he saith unto him, Verily, verily, I say unto you, Hereafter ye shall see heaven open, and the angels of God ascending and descending upon the Son of man.
(Serm. 40. [122.]) Nathanael remembered that he had been under the fig tree, where Christ was not present corporeally, but only by His spiritual knowledge. Hence, knowing that he had been alone, he recognised our Lord’s Divinity.