A prayer of healing that I can recite with clear conscience as a religious naturalist:
רוח העולם ומקור כל יקום
Lit. Spirit. Some new versions of blessings call God "Spirit of the World" (Ruakh Ha’olam), rather than "King of the World" (Melekh Ha'olam). ha’olam u’mekor kol yekum
Spirit of the universe and source of all nature
Illness and suffering are not punishments, but rather an inevitable part of life itself. Nature has provided our bodies with the means to keep us vital. We hope these will prove effective and that our doctors, nurses and other healers will have methods and insights to strengthen those means when the afflictions are too powerful for us to battle them alone.
We invoke the energy of the universe and express our gratitude for our health and wellbeing. We also think of our friends and relatives who are suffering. In particular, we think of … [names here]. We hope they will be restored to health, both physical and spiritual, in due time. We want them to know that we are thinking of them and will keep them in our mind continually. May they see release soon and may we continue to enjoy their company in better times. And for those with a terminal illness, we hope they will leave life with the gentle kiss of peace.