Alma 42:16

now repentance could not come unto men, except there were a punishment, which also was as eternal as the life of the soul should be, affixed opposite to the plan of happiness, which was as eternal also as the life of the soul.

People couldn’t repent unless there was a punishment. This punishment had to last forever, just like the soul lives forever. It stood against the plan of happiness, which also lasts forever.

Repentance couldn’t come to people unless there was a punishment as eternal as the soul’s life—set opposite to the plan of happiness, which was also as eternal as the soul’s life.