Nahum 1:9

What do ye imagine against the LORD? he will make an utter end: affliction shall not rise up the second time.

God will make an utter end of evil, affliction and rebellion, exterminating them so completely that suffering and sin will never appear or rise a second time.
This permanent end comes through Christ's redeeming work, by which sin will never again enter the universe.
It becomes safe only after the whole universe has witnessed the nature and results of sin, and God's character has been fully manifested as fathomless love and infinite wisdom, whereas at the beginning such action would have brought fear to angels and dishonor to God.

In that removal God's love and government are vindicated and His honor is established before beings who delight to do His will and have His law in their heart, Satan's charges are refuted, the law once reproached as bondage is honored as the law of liberty, and self-sacrificing love binds heaven and earth to their Creator in an enduring union.
After the final judgment and the eradication of evil, the tested and proved creation will remain loyal and will never again turn from allegiance to Him, secure from apostasy through the ages.

The destruction of Pharaoh and his host illustrates the end awaiting those who oppose God.
Therefore those admitted to the future world and the city of God must be reliable and obedient, prepared and sanctified in this life, since admitting those who disobey God and reject His terms would begin a second rebellion in heaven.