Ibn al-Qayyim (may Allah have mercy on him) said:
“Our Shaykh told me: I became ill, and the doctor said to me, ‘Your reading and speaking about knowledge is making the illness worse.’
So I said to him, ‘I cannot be patient without it. I will judge this matter according to your own knowledge: Is it not the case that when the soul becomes happy and pleased, the body’s natural strength increases and it repels illness?’
He said, ‘Yes.’
So I said, ‘My soul finds joy in knowledge. Because of it, the body gains strength and I feel relief.’
The doctor then said, ‘This is beyond the scope of our medicine.’”
Rawḍat al-Muḥibbīn (p. 109) by Imam Ibn al-Qayyim رحمه الله.