16 If anyone sees his brother commit a sin that does not lead to death, he should pray and God will give him life. I refer to those whose sin does not lead to death. There is a sin that leads to death. I am not saying that he should pray about that. 17 All wrongdoing is sin, and there is sin that does not lead to death.
I've heard this passage interpreted to mean that the sin that leads to death is apostasy or a sin against the Holy Spirit, not that adultery is worse than misuse of office supplies....
It doesn't say anything about apostasy. People interpret it how they want, but that's not what is said. It says there are sins bad enough to lead to death. Some aren't, and you should pray for your brother in that situation. Purely and simply written, that's what it says. Here it is in a number of translations for your perusal.
KJV
16If any man see his brother sin a sin which is not unto death, he shall ask, and he shall give him life for them that sin not unto death. There is a sin unto death: I do not say that he shall pray for it.
17All unrighteousness is sin: and there is a sin not unto death.
Youngs Literal translation
16If any one may see his brother sinning a sin not unto death, he shall ask, and He shall give to him life to those sinning not unto death; there is sin to death, not concerning it do I speak that he may beseech;
17all unrighteousness is sin, and there is sin not unto death.
NASB
16If anyone sees his brother committing a sin not leading to death, (A)he shall ask and God will for him give life to those who commit sin not leading to death (B)There is a sin leading to death; (C)I do not say that he should make request for this.
17(D)All unrighteousness is sin, and (E)there is a sin not leading to death
CEV
16Suppose you see one of our people commit a sin that isn't a deadly sin. You can pray, and that person will be given eternal life. But the sin must not be one that is deadly. 17Everything that is wrong is sin, but not all sins are deadly.
NKJV
16 If anyone sees his brother sinning a sin which does not lead to death, he will ask, and He will give him life for those who commit sin not leading to death. There is sin leading to death. I do not say that he should pray about that. 17 All unrighteousness is sin, and there is sin not leading to death.
Darby
16If any one see his brother sinning a sin not unto death, he shall ask, and he shall give him life, for those that do not sin unto death. There is a sin to death: I do not say of that that he should make a request.
17Every unrighteousness is sin; and there is a sin not to death
The Message
16For instance, if we see a Christian believer sinning (clearly I'm not talking about those who make a practice of sin in a way that is "fatal," leading to eternal death), we ask for God's help and he gladly gives it, gives life to the sinner whose sin is not fatal. There is such a thing as a fatal sin, and I'm not urging you to pray about that. 17Everything we do wrong is sin, but not all sin is fatal.
ESV
16If anyone sees his brother committing a sin not leading to death, he shall ask, and God[a] 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. 17All wrongdoing is sin, but there is sin that does not lead to death.