Who changed the truth of God - This is a repetition of the declaration in Romans 1:23, in another form. The phrase, “the truth of God” is a Hebrew phrase, meaning “the true God.” In such a case, where two nouns come together, one is employed as an adjective to qualify the other. Most commonly the latter of two nouns is used as the adjective, but sometimes it is the former, as in this case. God is called “the true God” in opposition to idols, which are called false gods. There is but one real or true God, and all others are false.
Into a lie - Into idols, or false gods. Idols are not infrequently called falsehood and lies, because they are not true representations of God; Jeremiah 13:25; Isaiah 28:15; Jeremiah 10:14; Psalms 40:4.
The creature - Created things, as the sun, moon, animals, etc.
Who is blessed forever - It was not uncommon to add a doxology, or ascription of praise to God, when his name was mentioned; see Romans 9:5; 2 Corinthians 11:31; Galatians 1:5. The Jews also usually did it. In this way they preserved veneration for the name of God, and accustomed themselves to speak of him with reverence. “The Muslims also borrowed this custom from the Jews, and practice it to a great extent. Tholuck mentions an Arabic manuscript in the library at Berlin which contains an account of heresies in respect to Islamism, and as often as the writer has occasion to mention the name of a new heretical sect, he adds, ‘God be exalted above all which they say’” (Stuart).
Amen - This is a Hebrew word denoting strong affirmation. So let it be. It implies here the solemn assent of the writer to what was just said; or his strong wish that what he had said might be - that the name of God might be esteemed and be blessed forever. The mention of the degrading idolatry of the pagans was strongly calculated to impress on his mind the superior excellency and glory of the one living God. It is mentioned respecting the honorable Robert Boyle, that he never mentioned the name of God without a solemn pause, denoting his profound reverence. Such a practice would tend eminently to prevent an unholy familiarity and irreverence in regard to the sacred name of the Most High; compare Exodus 20:7.