20 “How great” is “the multitude of Your sweetness, O Lord”. Here the Prophet exclaims, having sight of all this, and admiring how manifoldly plenteous is Your sweetness, O Lord. “Which You have hid for them that fear You.” Even those, whom Thou correctest, You love much: but lest they should go on negligently from relaxed security, Thou hidest from them the sweetness of Your love, for whom it is profitable to fear You. “You have perfected it for them that hope in You.” But You have perfected this sweetness for them that hope in You. For Thou dost not withdraw from them what they look for perseveringly even unto the end. “In sight of the sons of men.” For it does not escape the notice of the sons of men, who now live no more after Adam, but after the Son of Man. “You will hide them in the hidden place of Your Countenance:” which seat You shall preserve for everlasting in the hidden place of the knowledge of You for them that hope in You. “From the troubling of men.” So that now they suffer no more trouble from men.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)