John Gill Commentary Psalms 136:3

"Oh give thanks unto the Lord of lords; For his lovingkindness [endureth] for ever:" — Psalms 136:3 (ASV)

O give thanks to the Lord of lords
Which is not only the title of the God of Israel, as the former, (Deuteronomy 10:17); but of the Messiah, (Revelation 19:16); who is the Prince of the kings of the earth; under whom they are, by whom they reign, and to whom they are accountable, being higher than they; as nature, so by office, (Revelation 1:5) (Proverbs 8:15Proverbs 8:16) (Psalms 89:27);

for his mercy [endureth] for ever ;
in putting it into the hearts of kings and princes, which he has in his hands, to show favour to his people, even to be their nursing fathers; and in curbing the power, restraining the wrath, of oppressors; and protecting his people from their rage and violence.