15 Then follows, “I will exult for Your salvation:” that is, with blessedness shall I be holden by Your salvation, which is our Lord Jesus Christ, the Power and Wisdom of God. Therefore says the Church, which is here in affliction and is saved by hope, as long as the hidden judgment of the Son is, in hope she says, “I will exult for Your salvation:” for now she is worn down either by the roar of violence around her, or by the errors of the heathen. “The heathen are fixed in the corruption, which they made”. Consider ye how punishment is reserved for the sinner, out of his own works; and how they that have wished to persecute the Church, have been fixed in that corruption, which they thought to inflict. For they were desiring to kill the body, while they themselves were dying in soul. “In that snare which they hid, has their foot been taken.” The hidden snare is crafty devising. The foot of the soul is well understood to be its love: which, when depraved, is called coveting or lust; but when upright, love or charity....And the Apostle says, “That being rooted and grounded in love, you may be able to take in.” The foot then of sinners, that is, their love, is taken in the snare, which they hide: for when delight shall have followed on to deceitful dealing, when God shall have delivered them over to the lust of their heart; that delight at once binds them, that they dare not tear away their love thence and apply it to profitable objects; for when they shall make the attempt, they will be pained in heart, as if desiring to free their foot from a fetter: and giving way under this pain they refuse to withdraw from pernicious delights. “In the snare” then “which they have hid,” that is, in deceitful counsel, “their foot has been taken,” that is, their love, which through deceit attains to that vain joy whereby pain is purchased.
16. “The Lord is known executing judgments”. These are God's judgments. Not from that tranquillity of His blessedness, nor from the secret places of wisdom, wherein blessed souls are received, is the sword, or fire, or wild beast, or any such thing brought forth, whereby sinners may be tormented: but how are they tormented, and how does the Lord do judgment? “In the works,” he says, “of his own hands has the sinner been caught.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)