Give me your Puzzling Passages (modified)

I'd like to start a new collection: Puzzling Scripture. Submit your passages that, for you, resist a satisfactory explanation.

Of course, there are likely many such passages. However, if I had to pick just one, I think it'd be:

¹⁶ If anyone sees his brother committing a sin not leading to death, he shall ask, and God will give him life—to those who commit sins that do not lead to death. There is sin that leads to death; I do not say that one should pray for that. ¹⁷ All wrongdoing is sin, but there is sin that does not lead to death. (1 John 5:16-17)

No matter how many commentaries I read, or study-bible footnotes, I have yet to come across a parsing of this passage that smells right. For example, Matthew Henry, whom I find consistently reliable and understandable, writes, concerning this passage:

There is a sin unto death (v. 16), and there is a sin not unto death, v. 17. (1.) There is a sin unto death. All sin, as to the merit and legal sentence of it, is unto death. The wages of sin is death; and cursed is every one that continueth not in all things that are written in the book of the law, to do them, (Gal. 3:10). But there is a sin unto death in opposition to such sin as is here said not to be unto death. There is therefore, (2.) A sin not unto death. This surely must include all such sin as by divine or human constitution may consist with life; in the human constitution with temporal or corporal life, in the divine constitution with corporal or with spiritual evangelical life.

Say what?

Feel free to offer an explanation of this passage—but the main point for this post is to encourage you to submit your favorite puzzling scripture.