Back in the bible days in Jerusalem, there was a gate and it was called the eye of the needle. It was too small for a camel to go through unless you could get your camel down on his knees to crawl, and a person that was resourceful could possible do that. A rich man is usually caught up in his own self and thinks he has done all things with out giving credit to GOD. A humble man gives credit to GOD and ask for his help, this is a resource. SO in a nut shell it would be easier to get a camel to go through the eye of a needle than for a rich man to enter the kingdom (the kingdom is heaven).
So if Im not mistaken, this is what is being referenced here.
BTW, I agree with the article as well. Makes very good points. Just be prepared for what ever life throws your way.