What does the Bible say about inner renewal?

In 2 Corinthians 4:16, the Apostle Paul emphasizes the distinction between the outward and inward man. While our physical bodies experience decay and deterioration due to sin, the spiritual life that believers possess is sustained and revitalized by the Holy Spirit. This renewal is not based on our circumstances, but rather on God's grace, which provides strength and sustenance for our spiritual journey. As we confront trials and difficulties, it is through these experiences that our dependence on Christ deepens, allowing for a continual renewal of our inner selves. Paul himself exemplifies this dynamic, experiencing joy and strength despite external hardships.