The Mekhilta makes a claim that strikes against every human instinct: a person should rejoice in suffering more than in prosperity. The reasoning is startling in its logic. Even if someone lived in perfect comfort for an entire lifetime, basking in wealth and health and pleasure, none of that good fortune would erase a single transgression from their record. Sins committed during years of joy remain on the ledger, unpaid.
But affliction has a power that prosperity does not. Suffering atones. The Mekhilta states it bluntly: "Whereby are transgressions forgiven? By afflictions." Pain cleanses the soul in a way that pleasure never can. This is not masochism. The rabbis were not celebrating suffering for its own sake. They were making a theological argument about the economy of the spiritual world. In that economy, comfort is neutral at best. It does not move the needle on a person's standing before God. Affliction, by contrast, is active. It burns away the residue of sin.
This teaching became one of the foundations of the rabbinic concept of yissurin shel ahavah, "afflictions of love," the idea that God sends suffering to those He cherishes precisely because He wants to purify them. The person who suffers and accepts it with grace is not being punished. They are being refined. The Mekhilta asks its readers to flip their entire understanding of fortune on its head: the one who suffers has been given a gift that the comfortable person can only envy.