2 Corinthians 4:16
Therefore we don't faint, but though our outward man is decaying, yet our inward man is renewed day by day.
WEB
For which cause we faint not; but though our outward man perish, yet the inward man is renewed day by day.
KJV
What 2 Corinthians 4:16 means
Paul says that even as the body wears down, the inner life of a person can be renewed and strengthened every day.
Paul wrote this to the church in Corinth while defending a ministry full of hardship: beatings, exhaustion, danger. He is honest that his body was being worn out. But he insists something else was happening at the same time: an inner renewal, day by day, that suffering could not reverse.
He is not denying pain or pretending the body does not matter. He is describing two things running together, an outer decline and an inner strengthening, and staking everything on refusing to give up on the second.