The interpretation timeline
Psalm 117:20 Douay-Rheims

This is the gate of the Lord, the just shall enter into it.

A.D. 99 – 1771 5 witnesses

Patristic

before A.D. 750
99
A.D.
Clement of Rome Patristic
d. A.D. 99
“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. This is the gate of the Lord; the righteous shall enter in thereby." Seeing then that many gates are opened, this is that gate that is in righteousness, even that which is in Christ, whereby all are blessed who have entered in and direct their path in holiness and righteousness, performing all things without confusion. Let a person be faithful, let him be able to expound a deep saying, let him be wise in the discernment of words, let him be strenuous in deeds, let him be pure; for so much the more ought he to be lowly in mind, in proportion as he seems to be the greater; and he ought to seek the common advantage of all, and not his own.”
Source
346
A.D.
c. A.D. 270–346
“Our father Jacob too prayed at Bethel and saw the gate of heaven opened, with a ladder going up on high. This is a symbol of our Savior that Jacob saw: the gate of heaven is Christ, in accordance with what he said: "I am the gate of life; every one who enters by me shall live forever." David too said, "This is the gate of the Lord, by which the righteous enter." Again, the ladder that Jacob saw is a symbol of our Savior, in that by means of him the just ascend from the lower to the upper realm. The ladder is also a symbol of our Savior's cross, which was raised up like a ladder, with the Lord standing above it; for above Christ is the Lord of all, just as the blessed apostle said: "The head of Christ is God." Now Jacob called that place Bethel; and Jacob raised up there a pillar of stone as a testimony, and he poured oil over it. Our father Jacob did this too in symbol, anticipating that stones would receive anointing—for the peoples who have believed in Christ are the stones that are anointed; just as John says of them: "From these stones God is able to raise up children for Abraham." For in Jacob's prayer the calling of the nations was symbolized.”
Source
430
A.D.
Augustine of Hippo Patristic
A.D. 354–430
“But consider how the gates of righteousness are entered into. "These are the gates of the Lord" he saith, "the righteous shall enter into them" (ver. 20). At least let no wicked man enter there, that Jerusalem which receiveth not one uncircumcised, where it is said, "Without are dogs." Be it enough, that in my long pilgrimage "I have had my habitation among the tents of Kedar:" I endured even unto the end the intercourse of the wicked, but "these are the gates of the Lord: the righteous shall enter into them."”
Source

Scholastic

c. 1100 – 1500
1105
A.D.
Rashi Jewish
1040–1105
“This is the...gate of the Temple, which is the Lord’s, and the righteous will enter therein and there... I shall thank You because You answered me from the exile.”

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“This is the Lord's doing,.... This stone is from the Lord, Gen 49:24; it is of his choosing, appointing, and laying: the rejection of it by the builders is through his permission and will; they did no other things than what his hand and counsel determined should be done, Act 2:23; and the exaltation of it, or the making it the head of the corner, was of him; he highly exalted him at his right hand, above every name, creature, and thing; it is marvellous in our eyes; the stone itself is wonderful to look at, for its beauty, strength, and usefulness; the wisdom, love, care, and power of God, in laying it, are astonishing; the distinguishing grace of God in selecting some stones out of the common quarry, making them lively stones, and building them on this foundation stone, is exceeding marvellous: and so are both the rejection and exaltation of it; that so precious a stone should be refused, and, when treated with so much neglect and contempt, should be exalted. The Targum is, "from the Lord was this, said the builders; this is marvellous in our sight, said the sons of Jesse.''”
Source
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.