20 He hath put forth his hands against such as be at peace with him: he hath broken  his covenant.
20 My companion attacks his friends; he violates his covenant.
20 My companion
20 And this, my best friend, betrayed his best friends; his life betrayed his word.
20 He has put forth his hands against those who were at peace with him; He has broken his covenant.
20 As for my companion, he betrayed his friends; he broke his promises.
Matthew Henry's Commentary on Psalm 55:20
Commentary on Psalm 55:16-23
(Read Psalm 55:16-23)
In every trial let us call upon the Lord, and he will save us. He shall hear us, and not blame us for coming too often; the oftener the more welcome. David had thought all were against him; but now he sees there were many with him, more than he supposed; and the glory of this he gives to God, for it is he that raises us up friends, and makes them faithful to us. There are more true Christians, and believers have more real friends, than in their gloomy hours they suppose. His enemies should be reckoned with, and brought down; they could not ease themselves of their fears, as David could, by faith in God. Mortal men, though ever so high and strong, will easily be crushed by an eternal God. Those who are not reclaimed by the rod of affliction, will certainly be brought down to the pit of destruction. The burden of afflictions is very heavy, especially when attended with the temptations of Satan; there is also the burden of sin and corruption. The only relief under it is, to look to Christ, who bore it. Whatever it is that thou desirest God should give thee, leave it to him to give it in his own way and time. Care is a burden, it makes the heart stoop. We must commit our ways and works to the Lord; let him do as seemeth him good, and let us be satisfied. To cast our burden upon God, is to rest upon his providence and promise. And if we do so, he will carry us in the arms of his power, as a nurse carries a child; and will strengthen our spirits by his Spirit, so that they shall sustain the trial. He will never suffer the righteous to be moved; to be so shaken by any troubles, as to quit their duty to God, or their comfort in him. He will not suffer them to be utterly cast down. He, who bore the burden of our sorrows, desires us to leave to him to bear the burden of our cares, that, as he knows what is best for us, he may provide it accordingly. Why do not we trust Christ to govern the world which he redeemed?