1 Samuel 21:12 - Ellicott's Commentary On The Whole Bible

And David laid up these words. — Now, for the first time, David saw how widely travelled was a renown of which he in his humbleness of heart had thought so little, and at once a deadly fear took possession of him. The life he held so cheaply when in battle with the enemies of his country now, strange to say, in his deep degradation and poverty, became of real value to him, and he adopted the piteous and humiliating device of feigning madness, hoping thus to change the wondering admiration of the servants of Achish into pitying scorn. What David hoped took place, and he was driven out of Gath with ignominy; but there is no reason for supposing that had he maintained a quiet dignity of behaviour any evil would have happened to him. The Philistines, for those wild times, seem to have been a cultured people, and by no means devoid of generous instincts. Not one word, strangely enough, is reported to have been spoken about the great injury he had done to the Philistine nation when he slew Goliath. It has been suggested with considerable ingenuity that the great name of the dead champion, the hero of so many battle-fields, was never brought forward here, perhaps out of a natural indisposition to recall a grievous calamity, but more likely out of regard for Goliath’s family and friends. Singularly little is told us, in fact, about this renowned hero, whom tradition hints at as the great warrior in the decisive battle when the Ark was captured and the sons of Eli were slain. The Talmud has a curious comment on this strange silence — “Not half the praises of Goliath are related in Scripture; hence it follows that it is wrong to tell the praises of the wicked.” — Treatise Soteh, fol. 42, Colossians 2.