Chukat begins with the law of the Red Heifer, judged by the Sages to be the most incomprehensible in the Torah. It became a classic example of a chok, a “statute,” often understood as a law that has no reason, or at least none we can understand.
The text then shifts from law to narrative. After the death of Miriam the people find themselves without water. They complain to Moses and Aaron, who turn to God. They then respond to the people in a way that seems to suggest anger. They are judged to have acted wrongly, and both are told they will not enter the land. Aaron dies.
The people complain again and are attacked by venomous snakes. Moses, at God’s command, places a brass serpent on a pole, so that all who look up to it will be healed. The people sing a song about a Miraculous well that gave them water. Moses then leads the people into successful battles against Sichon and Og.