Proverbs 3:8 It shall be health to thy navel, and marrow to thy bones.
The conditional promise is typical to Proverbs: listen to Wisdom (Jesus), keep the commandments, trust in the Lord, and fear the Lord. Basically, keep the first commandment: “Fear, love, and trust in God above all things.” The other commandments follow from the First. The general principle is still often true: good living leads to good health. The Book of Job proves that “the doctrine of retribution” is not always going to hold up. The Lord has other reasons (which He doesn’t tell us) for why He allows diseases to come upon us.
We are still sinners, born in sin, and the relentless consequence is that we will die, and suffer many “little deaths” of disease and injury. Job learned the only answer: shut your mouth and repent and fear (believe in) the Lord.
The Lord always knows what He is doing. For one thing, He is more concerned about our spiritual health and eternal welfare. He knows how to use every affliction of body and soul in this temporal life to work in us a solid and permanent weight of glory. Such inward spiritual strengthening positively affects the outward man with life and health and every good thing. We are free to focus on the one thing needful, listening to Jesus, and let Him take care of everything else.