22 When, then, Nathanael had said “Whence know Thou me?” the Lord said to him, “Before that Philip called you, when you were under the fig-tree, I saw you.” O you Israel without guile, whosoever you are; O people living by faith, before I called you by my apostles, when you were under the shadow of death, and you saw not me, I saw you. The Lord then says to him, “Because I said unto you, I saw you under the fig-tree, you believe; you shall see a greater thing than these.” What is this, you shall see a greater thing than these? And He says unto him, “Verily, verily, I say unto you, you shall see heaven open, and angels ascending and descending upon the Son of man.” Brethren, this is something greater than “under the fig-tree I saw you.” For it is more that the Lord justified us when called than that He saw us lying under the shadow of death. For what profit would it have been to us if we had remained where He saw us? Should we not be lying there? What is this greater thing? When have we seen angels ascending and descending upon the Son of man?
Source: Tractates on the Gospel of John (New Advent)