Proverbs 26:18,19 - Joseph Benson’s Commentary on the Old and New Testaments

As a madman Hebrew, כמתלהלה, as one that makes, or feigns himself mad, in order that, under that pretence, he may do mischief with impunity; casteth firebrands, arrows, and death Any instruments of death and destruction against his neighbour's person, house, or goods; so is the man that deceiveth his neighbour That wrongs him under a false pretence of kindness and familiarity; and saith, Am I not in sport? And then asks his neighbour why he resents it so heinously, saying he was only in jest: and intended merely to try how he would take it.