Abstinence is the first medicine the human being must take, but for a complete cure the expenditure of mercy is required....Thus, although fasting repels the diseases of vice, excises the passions of the flesh, drives out what causes offenses; nevertheless, without the ointment of mercy, without the flow of kindness, without the practice of almsgiving, it does not restore complete health to the mind.
Sermon 41, section 3. The word for health here is 'salus', which can also mean 'salvation'.
