It is easier for a camel to go through the eye of a needle, than for a rich man to enter into the kingdom of God.
Note 7 at Mr 10:25: The Greek word for "needle," used in Mt 19:24 and here, is "RHAPHIS" and literally means "a needle" (Strong's Concordance).
The idea of applying "the eye of a needle" to a small door in a gate in the wall of Jerusalem seems to be a modern idea with no justification from the Hebrew or tradition. The reason for the Lord's statement about a camel going through the eye of a needle was to express the impossibility of those who trust in riches to enter into the kingdom of God. The disciples were overwhelmed with Jesus' statement and said, "Who then can be saved?" They understood Him to be talking of something that was impossible and not just difficult. Jesus' reply implied that the hearts of those who trust in riches could not be changed by man, but with God all things are possible.