Catena Aurea on Matthew 19:23–26: Gregory the Great

Or, by the rich man He intends any one who is proud, by the camel he denotes the right humility. The camel passed through the needle’s eye, when our Redeemer through the narrow way of suffering entered in to the taking upon Him death; for that passion was as a needle which pricked the body with pain. But the camel enters the needle’s eye easier than the rich man enters the kingdom of heaven; because if He had not first shewn us by His passion the form of His humility, our proud stiffness would never have bent itself to His lowliness.