According to a hadith, the Prophet Muhammad is said to have remarked: "For whomsoever of you the door of supplication is opened, for him the doors of mercy have been opened. And in God's eyes praying for good health is dearer to praying for anything else." (Sunan al-Tirmidhi, hadith no. 3548).
There is a saying that after faith, the greatest blessing we receive from God is good health. (Sunan Al-Kubra by An-Nasa'i 10651). Afiat here refers to good health. It's quite strange how human beings possess good health. As we all know that the human body has 78 organs, with 5 of them often referred to as vital organs: the brain, heart, lungs, liver, and kidneys. Human don't operate these 78 organs, they function continuously on their own. To keep the body in good shape, they work continuously day and night. However, humans have no control over it; they are all automatic machines. This body, which operates continuously with its 78 organs day and night, is entirely automatic. We visit doctors, hospitals, and engage in exercise. The contribution of all these activities to good health is less than 1%. God's part, also known as the Law of Nature, contributes more than 99%. It means that good health is something to be asked from God. Good health will only come if it is granted by God; otherwise, it won't.