2 Chronicles 16:12:

And Asa in the thirty and ninth year of his reign was diseased in his feet, until his disease was exceeding great: yet in his disease he sought not to the LORD, but to the physicians.

Notes on 2 Chronicles 16:12:

This verse has been used in some circles to “prove” that going to the doctor is a sin, but that error is handled elsewhere.  Asa’s problem wasn’t simply going to the doctor; it was not seeking the Lord.

See also:

Is It a Sin to Go to the Doctor or Take Medicine?
Condition: Foot Trouble