Clement of Rome

Let us therefore root this out quickly, and let us fall down before the Master and entreat him with tears, that he may show himself propitious and be reconciled to us and may restore us to the seemly and pure conduct that belongs to our love of the brothers. For this is a gate of righteousness opened to life, as it is written: "Open to me the gates of righteousness, that I may enter in thereby and praise the Lord. …

1 Clement 48 ↗

Augustine of Hippo

"Open me," he says, "the gates of righteousness" [Psalm 118:19]. Behold, we have heard of the gates. What is within? "That I may," he says, "go into them, and give thanks unto the Lord." This is the confession of praise full of wonder, "even unto the house of God, in the voice of joy and confession of praise, among such as keep holiday:" this is the everlasting bliss of the righteous, whereby they are blessed who dwell in the Lord's house, praising Him for evermore.

Exposition on Psalm 118 ↗

Bonaventure

If, now, it is considered as fulfilling or perfecting, this again is threefold: it may be seen as vital food for the militant and triumphant Church, as the punishment of crimes, and as the final reward. It is fitting that God be first; hence He is credible and understandable, and this in terms of influence by reason of the laws of mercy, justice and peace; in relation to the first, as Virtue; in relation to the second, as Truth; in relation to the third, as Equity. …

Collations on the Hexaemeron, Collation 10 ↗