See Wiersbe, pp. 174-175)
“He [God] had proved that He was able to provide water and food for them, so why were they quarreling with Moses? Because their hearts were still in Egypt!.
“Every difficulty God permits us to encounter will become either a test that can make us better or a temptation that can make us worse.” (Wiersbe, p. 174)
Compare above to Romans 8:28, and James 1:121-15.
The rod symbolized God's power.
A gracious God met the needs of a complaining people.
“Massah” means “to test” and “Meribah” means “contention, quarreling.”