Charles H. Spurgeon on Psalms 55:20

The psalmist cannot forget the traitor's conduct, and returns again to consider it. He hath put forth his hands against such as be at peace with him. He smites those to whom he had given the hand of friendship, he breaks the bonds of alliance, he is perfidious to those who dwell at ease because of his friendly profession. He hath broken his covenant. The most solemn league he has profaned, he is regardless of oaths and promises.