And every one that was in distress, and every one that was in debt, and every one that was discontented, gathered themselves unto him; and he became a captain over them: and there were with him about four hundred men.
Read Chapter 22
Ambrose of Milan
AD 397
For the just engage in many struggles. Does an athlete contend only once? How often, after he has won many victor’s crowns, is he overcome in another contest! How often it happens that one who has frequently gained the victory sometimes hesitates and is held fast in uncertainty! And it frequently comes to pass that a brave man is contending with brave men and greater struggles arise, where proofs of strength are greater. Thus, when David sought to flee to avoid the adversary, he also did not find his wings. He was driven here and there in an uncertain struggle.… But David is still in the cave—that is, in the flesh—in the cavern of his body, as it were, as he fights with King Saul, the son of hardness, and with the power of that spiritual prince who is not visible but is comprehensible. - "Flight from the World 5.28"
For if it is a bad thing to flee, it is much worse to persecute. The one party hides himself to escape death, the other persecutes with a desire to kill. It is written in the Scriptures that we ought to flee; but he that seeks to destroy transgresses the law and also is himself the occasion of the other’s flight. If then they [the Arians] reproach me with my flight, let them be more ashamed of their own persecution. Let them cease to conspire, and those who flee will immediately cease to do so. But they, instead of giving up their wickedness, are employing every means to obtain possession of my person, not perceiving that the flight of those who are persecuted is a strong argument against those who persecute. For no one flees from the gentle and the humane, but from the cruel and the evil-minded.
“Every one that was in distress and every one that was in debt” fled from Saul and took refuge with David. But this is the reason why these men [those persecuting Athanasius] desire to cut off...
When Christ stays among the humble, all the elect come down to him by humbling themselves. They come whether they are men, who are his brothers because he himself was made man, or angels, who are most of all his father’s house and the place of the dwelling of his glory. Also they come who are pressed down by the awareness of their sin and long by their bitter tears of penance to be washed and freed from their debt, that is, the debt of sin which the devil bestowed on them. With Christ as their leader, they hope to be brought into the joys of the kingdom.
“And about four hundred men joined him.” All who stand in the faith cling to the Lord, as they behave bravely, strengthen their hearts and are called to hope for, seek and obtain the realms of heaven through the teaching of the gospel. This doctrine is sealed in the most beautiful unity of the four books. The number hundred is often sought as the first fruitful number after so many preceding fruitless numbers, just as it is said that w...
Men. His title to the crown was incontestable, so that he might justly make war, particularly in his own defence, and receive those who flocked to him to screen themselves from the persecution of Saul, and from their debtors, whom they would thus enable themselves to repay in time, by the plunder which they would take from the enemy. David maintained the strictest discipline, and withheld his men from making any disturbance, always manifesting the greatest respect for the person of the king. (Calmet)
The soldiers of Jephte were of the same description as these of David, Judges xi. 3. (Haydock)