For some, saying “It’s in the hands of God” is kinda like saying I’m gonna dive into a pool with no water, then pray for rain.
My response to them is twofold: 1) Of course God’s got this, but 2) that does not preclude him using other means to heal, provide, fix, reconcile, et al. Ironically, failing to consider other means God may use suggests one does not actually trust God. You see, if God continues to care for creation providentially, then he may choose and most often does choose intermediary causes to bring about his good will for us. My experience shows me every day that human involvement is one of God’s strategies for bringing about what is good, whether in healing sickness or showing kindness to a stranger. God uses a variety of means as instruments to carry out his good will for his creatures. As C. S. Lewis once quipped, God “instituted prayer in order to lend to His creatures the dignity of causality” (“The Efficacy of Prayer”) and, while our prayers do not coerce or manipulate God into doing something he’s not already prepared to do, he does use prayer as a vehicle to execute what is best. Likewise, he may choose to employ the skill of a trained surgeon to supplement his goal of restoring health.
So, when I hear folk say, “God’s got this. He can heal,” I have no doubt about that. What I do find curious is whether he will do so directly or indirectly. There’s nothing wrong in expecting that God might use additional means to bring about good. In fact, it’s theologically responsible to think so!
There’s a story about a man who fell over a cliff but managed to grab hold of a tree branch to stop him falling to his death. He called out, hoping to attract the attention of someone who could help him: “Is there anyone there?” A voice came from the heavens: “Let go and I’II catch you.” The man thought for a moment and eventually called out, “Is there anyone else there?”
Addendum: It may not always be God’s will to heal. Just ask the child born to David and Bathsheba! The text says “the LORD struck the child that Uriah’s wife had borne to David, and he became ill” (see 2 Sam 12:15-18)