With the Israelites still ungrateful and grumbling, Moses has a very public meltdown.  His self-righteousness has caused him to become impatient with God's patient redemptive plan.  And we see that Moses is neither the hero of this story, nor the rescuer that God's people ultimately need.  God is the hero and he sends Jesus as our ultimate rescuer who gives us living water that finally quenches our thirst.