1 Samuel 18:25

The king desireth not any dowry It was customary in those times for the husband to give a present, or, as it is rendered, a dowry, to his father-in-law when he received his wife. But a hundred foreskins of the Philistines Saul made this demand of David, probably thinking that the necessity he would be under of attacking the Philistines at a disadvantage, or, at all hazards, in order to get the proposed number of foreskins within the time limited, would bring him into such dangerous encounters, as he could scarcely escape from. It is likely that Saul required the foreskins rather than the heads of the Philistines, to take away all possibility of David's deceiving him, by bringing the heads of such of his own men as might fall in battle, and passing them on him for the heads of the Philistines.