SALISBURY: It is great sin to swear unto a sin,
But greater sin to keep a sinful oath.William Shakespeare (1564-1616) English dramatist and poet
Henry VI, Part 2, Act 5, sc. 1, l. 186ff (5.1.186-187) (1591)
(Source)
swearing
In trying circumstances, urgent circumstances, desperate circumstances, profanity affords a relief denied even to prayer.
Mark Twain (1835-1910) American writer [pseud. of Samuel Clemens]
In Albert Bigelow Paine, Mark Twain: A Biography, ch. 38 (1912)
(Source)