The eye of a needle

From Gordon Fee in How to Read the Bible for All Its Worth: A Guide to Understanding the Bible (p. 22):

[I]n Mark 10:23 (Matt. 19:23, Luke 18:24), at the conclusion of the story of the rich young man, Jesus says, "How hard it is for the rich to enter the kingdom of God." He then adds: "It is easier for a camel to go through the eye of a needle than for a rich man to enter the kingdom." It is often said that there was a gate in Jerusalem known as the "Needle's Eye," which camels could go through only by kneeling, and with great difficulty. The point of this "interpretation" is that a camel could in fact go through the "Needle's Eye." The trouble with this "exegesis," however, is that it is simply not true. There never was such a gate in Jerusalem at any time in its history. The earliest known "evidence" for that idea is found in the eleventh century (!), in a commentary by a Greek churchman named Theophylact, who had the same difficulty with the text that we do. After all, it is impossible for a camel to go through the eye of a needle, and that was precisely Jesus' point. It is impossible for one who trusts in riches to enter the Kingdom. It takes a miracle for a rich person to get saved, which is quite the point of what follows: "All things are possible with God."