1 Samuel 18:27

Saul therefore gave his daughter Michal to him as a wife, etc. The unbelieving people could not prevent those predestined to life from believing. For they saw and understood that the Lord was in Christ, reconciling the world to himself; the love of the believers grew as much as the fear in the faithless. Some apply the foreskins taken from the struck Philistines by David to the condition of the present age, since the grace of Christ is at work among the Gentiles; however, the marriages of Michal, delayed for some time but eventually celebrated, refer to those who will believe at the end of the world, from the Jews: when the fullness of the Gentiles shall enter, so all Israel will be saved (Rom. XI).

And after a few days, David arose and departed, etc. A few days after the Jewish leaders decided to hand over Christ to be slain by the Gentiles, the Lord himself arose with the apostles who were with him to work the salvation of the world, shining so much with virtues and the grace of doctrine that, despite the efforts of the impious, he called not a few of the Gentiles to the grace of faith, as we have previously taught. For David struck down the Philistines, just as the Lord broke the proud impurity of paganism by word or by the example of humility and chastity. He brought their foreskins and counted them for the king so that he might be his son-in-law; with the people of the Jews, he showed the dead members of sin converted to God, so that in this way he might also receive those who would follow the conversion of the Gentiles. Not in vain did David bring two hundred foreskins to Saul, who had asked for one hundred; because, to the Jews presumptuously thinking that the Lord could not impose even the profession of carnal chastity on the Gentiles, he himself cleansed them from all defilement of flesh and spirit, perfecting sanctification in the fear of God. The number one hundred indeed always pertains to the indication of great perfection, which initiated in itself before the triumph of the Passion, was fulfilled even in the confirmation of his sacraments through the apostles after the clarification of his Assumption.