The same divine authority that forbids the killing of a human being establishes certain exceptions, as when God authorizes killing by a general law or when He gives an explicit commission to an individual for a limited time.
Saint AugustineDrunkenness is a flattering devil, a sweet poison, a pleasant sin, which whosoever hath, hath not himself, which whosoever doth commit, doth not commit sin, but he himself is wholly sin.
Saint AugustineIn no passage of the holy canonical books there can be found either divine precept or permission to take away our own life, whether for the sake of entering on the enjoyment of immortality, or of shunning, or ridding ourselves of anything whatever. Nay, the law, rightly interpreted, even prohibits suicide, where it says, 'Thou shalt not kill.' This is proved especially by the omission of the words "thy neighbor," which are inserted when false witness is forbidden.
Saint Augustine