Known sourcecanonical
"Dionysius the Elder, being asked whether he was at leisure, he replied, "God forbid that it should ever befall me!""
Plutarch / Apophthegms of Kings and Great Commanders. Dionysius.
Bartlett's Familiar Quotations, 9th ed. (Little, Brown, 1905), public domain
Bartlett's Familiar Quotations, 9th ed. (Little, Brown, 1905), public domain