If 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.
If someone sees their friend commit a sin not leading to death, they should ask for help, and it will be given to those who don't commit such serious sins. There is a sin leading to death; I am not saying one should pray for that.