Christ said "Blessed are the poor" in his Sermon on the Mount, which Lewis is fond of quoting. However, the complete sentence is, "Blessed are the poor in spirit: for theirs is the kingdom of heaven." Once again Lewis is being sloppy with exegesis; in this passage Christ clearly was not speaking of economic poverty.
On the other hand, the Gospels of Matthew, Mark, and Luke all relate Christ's reference to the difficulty of a rich person's entering the kingdom of God. His comments came after His encounter with the rich young ruler, and they clearly do relate to economic riches.
Matthew 19:23-24 (KJV): "Then said Jesus unto his disciples, Verily I say unto you, That a rich man shall hardly enter into the kingdom of heaven. And again I say unto you, 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."
Mark 10:23-27 (KJV): "And Jesus looked round about, and saith unto his disciples, How hardly shall they that have riches enter into the kingdom of God! And the disciples were astonished at his words. But Jesus answereth again, and saith unto them, Children, how hard is it for them that trust in riches to enter into the kingdom of God! 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. And they were astonished out of measure, saying among themselves, Who then can be saved? And Jesus looking upon them saith, With men it is impossible, but not with God: for with God all things are possible."
Luke 18:18-30 (KJV):
"And a certain ruler asked him, saying, Good Master, what shall I do to inherit eternal life? And Jesus said unto him, Why callest thou me good? none is good, save one, that is, God. Thou knowest the commandments, Do not commit adultery, Do not kill, Do not steal, Do not bear false witness, Honour thy father and thy mother. And he said, All these have I kept from my youth up. Now when Jesus heard these things, he said unto him, Yet lackest thou one thing: sell all that thou hast, and distribute unto the poor, and thou shalt have treasure in heaven: and come, follow me. And when he heard this, he was very sorrowful: for he was very rich. And when Jesus saw that he was very sorrowful, he said, How hardly shall they that have riches enter into the kingdom of God! For it is easier for a camel to go through a needle's eye, than for a rich man to enter into the kingdom of God. And they that heard it said, Who then can be saved? And he said, The things which are impossible with men are possible with God. Then Peter said, Lo, we have left all, and followed thee. And he said unto them, Verily I say unto you, There is no man that hath left house, or parents, or brethren, or wife, or children, for the kingdom of God's sake, Who shall not receive manifold more in this present time, and in the world to come life everlasting."