For the arms of the wicked shall be broken - See the notes at Psalms 10:15. The “arm” is the instrument by which we accomplish a purpose; and the meaning here is, that that will be broken on which the wicked rely, or, in other words, that their plans will fail, and that they will be disappointed - as a man is rendered helpless whose arms are broken. Compare the notes at Job 38:15.
But the Lord upholdeth the righteous - The Lord will sustain and strengthen him. While the plans of the wicked will be defeated, while they themselves will be overthrown, and fail to accomplish their purposes of wickedness, the Lord will uphold the righteous, and enable them fully to carry out their plans. Their great scheme or purpose of life, the promotion of the glory of God, and the salvation of their own souls, will be fully accomplished - for in that purpose God will be their helper and friend.