The text of Numbers 21 concerns the snakes that bit the people of Israel after they grumbled against Moses and the Lord. In an act that would foreshadow the salvation that Jesus would bring, Moses lifted up a bronze snake upon a pole and all who looked to it were healed and kept from certain death. Jesus spoke of this in John 3:15-18 and said that He would be lifted up (on the cross) and all who look to Him in faith will be saved.