1 Samuel 21:13

For behold David the prophet also in his scheme for delivering his life from death feigned himself to the Philistines to be a madman and without sense, and let his spittle fall down upon his beard after the manner of a man who lacked understanding, that he might save his life from death. And if David feigned himself to be mad, and to be without understanding and discretion that he might not destroy his life in this world, how much more is it meet for thee to abide in thy simplicity, and not to be overcome by the indignation of the scoffers, and not to depart from the goal which is laid down for thee, for the sake of life everlasting?

When Saul was pursuing David, David fled to king Achish, and since through the motive of jealousy he was suspected there, he carefully changed his countenance, covering his face with spittle so that he would be thought to be diabolically possessed and thus released unharmed as an object of pity. But these and other deeds were accomplished by David as evidence of a great mystery, for he showed that the spittle, which represented the holy Scriptures, was running down his beard, that is, had great strength. The significance of these things led to the substitution of the name of Abimelech, meaning "kingdom of my father," for Achish, to whom David had fled. Clearly this incident aptly refers to the Lord Christ, through whom the glorious Father with most holy devotion undertook service to the world. The expression "who dismissed him" refers to king Abimelech; "and he went his way" means that David departed to another region because, as we have said, he had begun to be suspected.

All these modes of expression will be thought lies, if a figurative expression or action is to be considered a lie. But, if it is not a lie when signs signifying one thing are put for another to serve the understanding of a truth, certainly that should not be judged a lie either which Jacob did or said to his father in order to be blessed, or what Joseph said in sporting with his brothers, or David's pretense of insanity, or other signs of the same kind. They should be judged as prophetic expressions and actions set forth for the understanding of those things which are true. Those things are veiled in figures, in garments as it were, in order that they may exercise the mind of the pious inquirer and not become cheap for being bare and obvious. Although we have learned their meaning stated openly and plainly in other places, still, when they are dug out of obscurity, they are somehow recreated in our knowledge and thus become sweet. A student is not hindered because they are shrouded in this way. On the contrary, they are rendered more acceptable: for being remote they are more ardently desired, and for being desired they are more joyfully discovered.