4 And so, since these words are understood to be inapplicable to the divinity of the Only-begotten Son of God, our Lord Jesus Christ, we must suppose him, who is here extolled as happy by the Prophet, to be the man who strives to conform himself to that body which the Lord assumed and in which He was born as man, by zeal for justice and perfect fulfilment of all righteousness. That this is the necessary interpretation will be shown as the exposition of the Psalm proceeds.
Source: Homilies on the Psalms (New Advent)