Augustine of Hippo

In this way, too, the kingdom of Saul himself, who certainly was reprobated and rejected, was the shadow of a kingdom yet to come which should remain to eternity. For, indeed, the oil with which he was anointed, and from that chrism he is called Christ, is to be taken in a mystical sense, and is to be understood as a great mystery; which David himself venerated so much in him, that he trembled with smitten heart when, being hid in a dark cave, which Saul also entered when pressed by the necessity of nature, he had come secretly …

The City Of God 17.6 ↗

Bede

After these things, David's heart struck him, etc. The Lord groaned for the human race, from which he took flesh, with the affection of compassion, because by its merits he was compelled to take away some part of its royal ornament, preferring that it might have the kingdom here and always in the future age, preserved by divine law. Finally, seeing the sinful city, he wept over it saying: For if you also had known, and the rest (Luke 19). …

Commentary on Samuel ↗