"But for you who fear my name, the sun of righteousness will rise with healing in its wings." Malachi 4:2
Righteousness brings healing, just as unrighteousness brings death and destruction.
The imagery here represents the coming promised One, the Lord Jesus Christ, who brought in everlasting righteousness and undid the destruction our unrighteousness brought with it. He is our righteousness (Jeremiah 23:5-6).
The LORD warned Adam, “In the day that you [sin] you shall surely die.” (Genesis 2:17). Sin brings death. It is most evident then that righteousness brings life. In fact Paul says this very plainly: “Just as sin reigned in death, grace also [reigns] through righteousness leading to eternal life through Jesus Christ our Lord” (Romans 5:21).
If we are to be healed, body and soul, we must have righteousness. We don’t. But the God of grace and mercy loved us and sent his Son to provide us with the righteousness he requires from us. The result is that, if we trust in Christ, his spotless perfection is imputed to us, is considered ours, and we get treated accordingly, because it is ours in Christ.
So the healing starts now, and will be finished when the sun of eternal day rises on a new creation. Death is being undone. All who trust in Christ are even now new creatures within, and will be brought to completed newness, body and soul, in glory when we will stand (and run and jump and, who knows, even fly) in resurrected bodies on a resurrected planet in a resurrected universe, "in which righteousness dwells" (2 Peter 3:13). In other words, we will be "swallowed up by life" (2 Corinthians 5:4).