David refuses to allow those around him to harm King Saul, expressing absolute faith that God will bring about the king's end without any need for human intervention. He outlines three distinct ways a person's life can conclude, establishing that Saul's reign will soon finish through Divine providence rather than assassination.
To emphasize his certainty, David takes a solemn oath. This vow underlines that Saul will not live much longer, either because God has already rejected him and anointed David in his place, or because the prophet Samuel had directly informed David of this impending end [רד״ק, אברבנאל, אלשיך, מצודת דוד]. Alternatively, the oath serves a more immediate, practical purpose: David is either swearing against his own impulses to ensure he restrains himself, or he is issuing a severe warning to his companion Abishai, threatening that if Abishai kills Saul, David will execute him in return [רש״י, רד״ק, אברבנאל].
The first possibility David raises for Saul's demise is that God might actively hasten his death [רש״י], striking him down prematurely with a sudden illness [רד״ק, ביאור שטיינזלץ, מצודת דוד, אברבנאל]. Such an end serves as a direct punishment for a person's sins, similar to the sudden fate that befell Nabal the Carmelite [רלב״ג, רד״ק, אלשיך]. In this scenario, a person's transgressions cause God's attribute of mercy to transform into strict justice, which then strikes the individual [חומת אנך].
The second scenario is that a person reaches the exact lifespan allotted to them from birth, passing away naturally without any sudden plague or illness [רש״י, רלב״ג, מצודת דוד, ביאור שטיינזלץ]. David reasons that even if Saul possesses certain merits that protect him from a sudden Divine strike, his natural end must still be rapidly approaching. Since one royal dynasty cannot overlap with another, and David has already been anointed as the new king, Saul's time must be running out [אלשיך]. In the case of a natural death, any ultimate punishment for the person's sins is simply delayed until after they pass away [חומת אנך].
The final possibility is a premature death brought about by a person's own choice to enter a dangerous environment, such as going into battle and meeting complete destruction [רלב״ג, מצודת ציון]. While some view dying in war as a matter of tragic chance [אברבנאל], others stress that such a death is not accidental at all. Rather, it serves as a severe punishment for exceptionally grave sins, such as Saul's massacre of the priests of the city of Nob [רד״ק, אלשיך]. Furthermore, the very act of going to war places a person in a state of intense vulnerability, granting forces of impurity and strict judgment the permission to accuse and punish them [חומת אנך].