Deuteronomy 1:18

And I commanded you at that time all the things which ye should do.

Moses commanded Israel at that time all the things they were to do, as he recounted their experiences in order to teach them to follow the principles God had given them. That command set forth the duties of judges and appointed leaders to hear cases, to judge righteously without partiality and without fear of man, and to bring causes too hard for them to Moses. The people had agreed to follow these directions.

Their later murmuring and rebellion was therefore disobedience to what they had promised to follow and to guidance God had given for their good. Obedience and cooperation with God's plans were necessary for their good and eternal welfare. God's promises in the surrounding chapter were conditional on obedience, so failure to obey and trust God kept the adults who came out of Egypt from being brought into the promised land. Caleb and Joshua were the exceptions, because they wholly followed the Lord.

The instruction is the Lord's own words and admonition for later generations. That admonition calls readers to follow God's direction rather than insist on human judgment.