Compare Eph. 3:20. David is here thinking primarily, if not altogether, of the cup of joy of the Lord. God gives unstintingly of His mercies, pressed down and running over. In a secondary sense the figure may describe the blessings of material prosperity. David had enjoyed such blessings. He also learned through hard experience that prosperity is dangerous to spiritual life. “The cup most difficult to carry is ... the cup that is full to the brim” (MH 212). Even harder, if possible, is it to carry the cup that “runneth over.”
Of mine enemies.
Since God is the host, the plots of the enemies to injure must come to nought.
Preparest a table.
David now represents himself as a guest in God’s banquet hall. Jehovah is even more than a shepherd—He is a king, lavishing upon His guests the bounties of His table. Compare the parable of the marriage of the king’s son (Matt. 22:1-14). The phrase “preparest a table” is idiomatic for preparing a meal (see Prov. 9:2).