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. All wrongdoing is sin, but there is sin that does not lead to death. -ESV
I like the ESV translation of this a lot. The big thing is in the beginning of verse 16, with ask and give, it keeps it in the future tense, and, most importantly, keeps the word ask instead of changing it to pray. The verb there is aiteo which is the same verb that has been used in the previous verses promising that we will be given anything which we ask of God. This is clearly intended to be an example of this promise.