Why does David call Doeg a liar in Psalm 52?
Why does David call Doeg a liar, when he told Saul truth (although with evil intention) about David coming to Ahimelech the priest?
Samuel Ridout addresses this directly:
Samuel Ridout"Doeg, intentionally or otherwise, misrepresents David's interview with Ahimelech. From David's characterization of it in Psalm 52, there can be little doubt that his own enmity led him deliberately to lie. Whatever would weaken the kingdom of Israel would be pleasing to an Edomite. According to his representation, Ahimelech was in the conspiracy to enthrone David. He had inquired of the Lord for him, had given him food and the sword of Goliath but even the statements which were correct were given a wrong interpretation by Doeg, and so his whole narrative was false witness, which had a most disastrous result for the priestly house."
The raw facts Doeg reported were partly correct, but he framed them to create a false narrative — that Ahimelech was conspiring with David against Saul. The truth was that Ahimelech innocently helped a man he had no reason to suspect was a fugitive.
Leslie Grant reinforces this:
Leslie Grant"His tongue is his most powerful weapon, able to twist truth so that it appears to be commending falsehood. ... his tongue devises destruction, like a sharp razor, cutting deceitful hatred (v. 2)."
Hamilton Smith writes similarly:
Hamilton Smith"His words may, to the unwary, appear fair; but they are devised to work mischief, like a sharp razor that cuts before one is aware. Thus he will be marked by 'practising deceit' ... he loves evil rather than good ... he loves 'lying rather than to speak righteousness' ... he loves 'devouring words'"
So Doeg's lie was not in the bare facts he reported, but in the malicious interpretation he put upon them. He used true details to construct a false accusation — that the priest was a conspirator — which is itself a form of lying ("false witness"). His tongue worked "like a sharp razor" (v. 2), cutting with deceit: technically accurate words weaponized to achieve a murderous end.