शिवपुराण - वैद्य

निदानज्ञस्य भिषजो रुग्णहिंसां प्रयुंजतः ।
न किंचदपि नैर्घृण्यं घृणैवात्र प्रयोजिका ॥

- शिवपुराण

A doctor diagnoses a problem correctly and makes the patient go through the pain of surgery. There is no sin attached to this. In fact, he gets a lot of good karma credit for this.

- Shivapurana