In the Old Testament account of Moses leading the Israelites into the Promised Land, having been slaves in Egypt for hundreds of years, they started turning against God. This was in spite of the success they were having in destroying enemies, because of God's help, in order to get full control of the Promised Land. They were also complaining that their provisions weren't ample enough. Are we ever like that, complaining to God about His inadequacies and the fact that He is not giving us exactly what we want, forgetting how much He has already done for us? Sometimes we might even want to turn our backs on Him completely. In that place of rejecting God, poisonous snakes with fatal bites entered the Israelite's camp. They repented and, on God's merciful instruction, by looking at a bronze snake on a pole they were saved. (Book of Numbers Chapter 21). Can you see the parallel with Jesus carrying our sin on the Cross? Look to Him and be saved.
