Quote from : Life of Christ Book

The Book of Numbers relates that when the people murmured rebelliously against God, they were punished with a plague of fiery serpents, so that many lost their lives. When they repented, Moses was told by God to make a brazen serpent and set it up for a sign, and all those bitten by the serpents who looked upon that sign would be healed. Our Blessed Lord was now declaring that He was to be lifted up, as the serpent had been lifted up. As the brass serpent had the appearance of a serpent and yet lacked its venom, so too, when He would be lifted up upon the bars of the Cross, He would have the appearance of a sinner and yet be without sin. As all who looked upon the brass serpent had been healed of the bite of the serpent, so all who looked upon Him with love and faith would be healed of the bite of the serpent of evil.