Thou shalt not curse the deaf. The sin of cursing another is in itself complete, whether the curse be heard by that other or not, because it is the outcome of sin in the speaker's heart. The suffering caused to one who hears the curse creates a further sin by adding an injury to the person addressed.
Strangely in contrast with this is not only the practice of irreligious men, who care little how they curse a man in his absence, but the teaching which is regarded by a large body of Christians as incontrovertible.
"No harm is done to reverence but by an open manifestation of insult. How, then, can a son sin gravely when he curses his father without the latter's knowing it, or mocks at him behind his back, inasmuch as in that case there is neither insult nor irreverence?
And I think that the same is to be said, even though he does this before others. It must be altogether understood that he does not sin gravely if he curses his parents, whether they are alive or dead, unless the curses are uttered with malevolent meaning.'
' This is the decision of one that is called not only a saint, but a "doctor of the Church" (Liguori, 'Theol. Moral.,' 4.334). "Whoso curseth his father or his mother, his lamp shall be put ant in obscure darkness," says the Word of God (Proverbs 20:20).
Nor put a stumbling block before the blind, but shalt fear thy God. By the last clause the eye is directed to God, who can see and punish, however little the blind man is able to help himself. (Cf. Job 29:15, "I was eyes to the blind, and feet was I to the lame."