Numbers 32:8

Thus did your fathers, when I sent them from Kadesh-barnea to see the land.

Moses was speaking to the children of Gad and Reuben after they asked to settle east of the Jordan, warning them not to discourage Israel from going over into the land the Lord had given them. He feared their request meant avoiding the conflicts of taking Canaan, and that such unbelief and cowardice would bring the Lord's displeasure. The fathers sent from Kadesh-barnea to see the land went up to the valley of Eshcol and saw the land, and then discouraged their brethren and the heart of Israel from entering it.

That discouragement stirred the wrath of a jealous God so that His anger was kindled against them. He swore that none of the men from twenty years old and upward who came out of Egypt would see the land sworn to Abraham, Isaac, and Jacob, because they had not wholly followed Him. Only Caleb and Joshua were excepted, because they wholly followed the Lord, while He made Israel wander forty years until that evil generation was consumed, thus shutting that generation out of the promised land. God's promises are upon condition of obedience.

Moses warned the new generation risen up in their fathers' stead that as an increase of sinful men they would augment His fierce anger. If they turned away He would yet again leave Israel in the wilderness and destroy the people. Gad and Reuben promised to fight alongside their brethren until all had received their inheritance, and Moses warned that if they failed to keep that promise their sin would find them out.

As ancient Israel's disobedience hindered entry, the same disobedience, unthankfulness, and unholiness in God's people now hinders God's work and keeps the messages of truth from being borne to all people. Had they walked in His counsel, believed Him, been doers of His word, and kept His commandments the work would have advanced without delay. Instead their failure prolongs time and delays the sealing time of God's servants. Yet a longsuffering God bears with their sins so that many who have not heard the truth may hear the last message of mercy proclaimed with a loud voice, be converted, and the great work go forward.