John Calvin Commentary Psalms 55:20

"He hath put forth his hands against such as were at peace with him: He hath profaned his covenant." — Psalms 55:20 (ASV)

He hath sent his hands against those that were at peace with him. He afterward speaks in Psalm 55:23d in the plural number, but here it is probable that he begins by addressing the leader and head of the wicked conspiracy. He accuses him of waging war in the midst of peace, and being thus guilty of a breach of faith.

He had neither suffered provocation, nor had he announced in an open manner his intention to give battle, but had commenced the attack unexpectedly and with treachery. The same charge is insisted upon further, when it is added, that butter and oil were in his lips, while war was in his heart, and his words themselves were darts.

In appearance they were soft and agreeable, but they covered a hidden virulence and cruelty which wounded like a sword or like darts, according to the common proverb, that deceivers carry on their lips poison smeared with honey. It is well known how many fair promises and flatteries Saul addressed to David to entrap him, and we may conjecture that the same arts were practiced by his courtiers.

It is one special trial of the Lord’s people, that they are exposed to such attempts on the part of crafty men to seduce them into destruction. Here the Holy Spirit puts a mark of reprobation upon all subtlety of this kind, and particularly upon treacherous flatteries, exhorting us to cultivate simplicity of intention.