The interpretation timeline
Psalm 116:2 Douay-Rheims

For his mercy is confirmed upon us: and the truth of the Lord remaineth for ever.

A.D. 430 – 1849 4 witnesses

Patristic

before A.D. 750
430
A.D.
Augustine of Hippo Patristic
A.D. 354–430
“"For His merciful kindness is ever more and more towards us: and the truth of the Lord endures for ever." These are those two things, loving-kindness and truth, which in the CXVth Psalm I admonished you should be committed to memory. But "the merciful kindness of the Lord is ever more and more towards us," since the furious tongues of hostile nations have yielded to His Name, through which we have been freed: "and the truth of the Lord endures for ever," whether in those things which He promised to the righteous, or in those which He has threatened to the ungodly.”
Source

Scholastic

c. 1100 – 1500
1105
A.D.
Rashi Jewish
1040–1105
“For His kindness has overwhelmed us That is to say: and surely we [must praise Him], for His kindness has overwhelmed us. and the truth of the Lord is eternal For He kept His promise that He promised the Patriarchs.”

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“For his merciful kindness is great towards us,.... Not us Israelites only, of whom David was, but Gentiles also; or otherwise there would be no force in the reason why all people and nations should praise the Lord: but it respects the time when these should become one people, partaking of the same grace, blessings, promises, and privileges; in which the grace, mercy, and lovingkindness of God, greatly appeared; "it prevailed over us" (p), as it may be rendered: the word is used of the prevailing of the waters of the flood over the earth, Gen 7:18; and so may denote the exuberance of the grace of God, of the abounding and superabounding of it. There is an abundance of it in the heart of God, in his covenant, and in his Son; and which is displayed in redemption by him; in the forgiveness of sin; and in the conversion of sinners, and their everlasting salvation: particularly there has been an inundation or deluge of it in the Gentile world, where it has flowed and overflowed; where sin abounded, grace has much more abounded; and therefore the Lord is to be praised. And another reason follows, and the truth of the Lord endureth for ever; the faithfulness of God to his promises, not only made to the Jewish fathers concerning the Messiah, and redemption by him; but to the Gentiles, and concerning the blessing of all nations in the promised seed: and the faithfulness and truth of God, with respect to any of his promises, never fails; nor will his word of truth, the Gospel; nor Jesus Christ, who is the truth, and the truth of God; the truth of types, promises, and prophecies; see Psa 43:3; for he is the same today, yesterday, and for ever. Praise ye the Lord; for his superabounding grace, and eternal truth; even all the people of God, of all nations, Jews and Gentiles. (p) "exsuperavit", Vatablus; "invaluit", Junius & Tremellius, Piscator, Gejerus, Michaelis; "exuberavit", Cocceius. Next: Psalms Chapter 118”
Source
1849
A.D.
1774–1849
“Remaineth is not in Hebrew. Mercy and truth confirm us. (Haydock) — The psalmist acknowledges that he also stands in need of them, and St. John assures us, that grace and truth came by Jesus Christ. [John i. 17.] (Berthier) — No promise had been made to the Gentiles (Worthington) by the law; though they were all included in the original promise, Genesis iii. 15. (Haydock) — God hath withdrawn them from idolatry, to impart to them his mercies. (Calmet) Bible Text & Cross-references: All nations are called upon to praise God for his mercy and truth. 1 Alleluia. O praise* the Lord, all ye nations: praise him, all ye people. 2 For his mercy is confirmed upon us: *and the truth of the Lord remaineth for ever.”
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.