David is reeling from the news of Ish-bosheth's murder. This wasn't just any death; it was a brutal act of treachery by his own men against a king, even a weak one.
A Shocking Act of Treachery
David's words here aren't just anger; they express profound horror. Ish-bosheth, though not a righteous king in David's eyes, was still the anointed ruler of Israel. His assassins, Baanah and Rechab, murdered him in his own home, in his bed, while he was at his most vulnerable. This was a violation of trust, safety, and kingship.
The Principle of Accountability
David immediately invokes the principle that blood cries out for justice. The murder was so heinous, so against the natural order and any sense of honor, that David, as the future king, feels compelled to act. He knew that allowing such a wicked deed to go unpunished would set a dangerous precedent and invite divine judgment.