Majjhima Nikaya 4:70
SUJATOYañhissa, bhikkhave, cakkhundriyasaṁvaraṁ asaṁvutassa viharato uppajjeyyuṁ āsavā vighātapariḷāhā, cakkhundriyasaṁvaraṁ saṁvutassa viharato evaṁsa te āsavā vighātapariḷāhā na honti.
For the distressing and feverish defilements that might arise in someone who lives without restraint of the eye faculty do not arise when there is such restraint.