1 Corinthians 1:21-29. I'll just italicize the forged part and let you think for yourself.

21 For since in the wisdom of God the world hasn't known God through the wisdom, God has been pleased through the foolishness of the proclamation to save those who have faith. 22 Since Jews ask for signs and Greeks seek wisdom, 23 but we proclaim Anointed (Christ) staked (crucified), to Jews a stumbling block and to nations foolishness; <24 but to the called, both Jews and Greeks, Anointed is power of God and wisdom of God. 25 Because the foolishness of God is wiser than humans, and the weakness of God is stronger than humans. 26 For look at your calling brothers; because not many are wise according to flesh; not many are powerful; not many are nobles.> 27 but the foolish things of the world God chose so he could shame the wise, and the weak things of the world God chose so he could shame the strong, 28 and the unborn things of the world [and the despised things] God chose, the things that are not, so he could make the things that are cease. 29 That way all flesh cannot boast.

How do we know it's a forgery? Well there is some strange terminology like "the called", but mainly, oh I don't know, maybe it's because it's going out of its way to contradict itself and shift the embarassing statements onto something else entirely.

Luckily for whoever decided to do this, "unborn" can also mean not of high class or nobility. But we know for a fact this isn't the meaning intended in verse 28, because it specifies "the things that are not".

If Paul wrote the original piece here, it means that, at least at the time, he may have been a mythicist, since he called both the gospel and the cross "unborn" and "things that are not". Of course he's not calling it fake or trying to insult it, but he may have believed it happened in a different realm than our own.

Update: I have decided to bracket the words "and the despised things". I think the redactor probably added it to fit his reinterpretation of ἀγενῆ, because it does not really fit here. Notice how "the things that are not" remains. Scribes rarely ever removed text, but they freely added material to explain away what they didn't like. It doesn't really matter though, because the meaning isn't affected without verses 24-26, it's just a little awkward and out of place.