There are two stories in this one chapter. The first is about Moses smiting a rock and it bringing forth water. The second is about Moses blessing Israel as they fought the Amalekites. Let's treat them separately.
1. A Rock Full of Water: The first notable event here is the complaint of the Israelites. And it was so unoriginal. In fact, this was the fourth such case in a row (Exodus 14:11-12; 15:24; 16:3 & 17:3). So far, every time they encountered difficulties or uncertainties, they immediately resorted to self-destructive, tetchy strategies.
But, again, regardless of their very poor disposition, God was there to help them (I Corinthians 10:4). They needed water... so now for the third time and by yet another method, He quenched their thirst. (Exodus 17:6). This time Moses struck "the rock of God" and 2 things happened. First, it miraculously produced water for the nation and, second, it produced an example for the nation. Some of the people were to come to understand the full significance of the smiting of that rock many years later. God was moving towards the striking of THE ROCK which would produce eternal life-giving spiritual water.