And to make plain to everyone the administration of this mystery, which for ages past was kept hidden in God, who created all things. (NIV)
This verse is not a problem in most translations, because most do not have the phrase, “by Jesus Christ,” at the end of the verse. Apparently this phrase was added to some Greek manuscripts as debates about the Trinity caused some scribes to “augment” their position by adding to the Word of God, or it could have been a marginal note that was accidentally copied into some manuscripts. It is not well supported in the textual tradition. A Textual Commentary on the Greek New Testament notes that the omission of the phrase is “decisively supported” by the texts, as well as by the “early patristic quotations” (i.e., the places where the Church Fathers quoted the verse). For more information about how Trinitarian information was added, see the notes on 1 John 5:7-8.