Numbers 32:13

And the LORD’s anger was kindled against Israel, and he made them wander in the wilderness forty years, until all the generation, that had done evil in the sight of the LORD, was consumed.

The forty years of wandering led through harsh, barren country that brought heat, dust, thirst, and fatigue, drawing complaints and sighs from the people, though they murmured less than many travelers would have under the same conditions. The Lord's anger was kindled against Israel because of the evil done in His sight, namely repeated murmuring and rebellion. As punishment He made them wander in the wilderness forty years until the whole evil generation was consumed.

None of the men who came up out of Egypt from twenty years old and upward would see the land sworn to Abraham, Isaac, and Jacob, except Caleb and Joshua because they wholly followed the Lord. The adults who had left Egypt, except for two, died before entering the promised land, their journey prolonged until that generation was gone. The verse shows that the Lord is a jealous God who bears long with the sins of His people, yet His promises are upon condition of obedience. So He alters His purpose and withholds what He promised when His people do not wholly follow Him.

The verse warns that God sees and judges selfishness, avarice, and deception, and that cherished sin will bring His displeasure and its consequences. Like ancient Israel, the disobedience, unthankfulness, and unholiness of God's people in this generation has hindered His work and prolonged time, delaying the sealing time when the four winds are held back. Had God's people believed Him, been doers of His word, kept His commandments, and walked in His counsel, the work would have advanced and the messages of truth would have been borne to all people on the earth. Then there would have been no need for the command to the four angels to hold the four winds until the servants of God are sealed.

Because of disobedience like ancient Israel's, time is prolonged in mercy so that many who have not heard the truth may have opportunity to hear the last message of mercy proclaimed with a loud voice, be converted, and the great work of God go forward.