Answer:
Their obligation to God in the covenant relationship.
Step-by-step explanation:
Moses was one of the great Judge or leader and he was the one that God used to lead the Israelites out of slavery in the land of Egypt.
What saddens one is the fact that even after the first generation of Israelites saw the miracles and the power of God, it was recorded that at any slight inconveniences or test that they face in the wilderness, they use that to turn away from the Lord and murmured and grumbled against the Lord's Chosen -- Moses and his brother; Aaron.
Moses wasted no time in making sure that he reminds the first generation of Isrealites about their obligation to God in the covenant relationship.