If any man see his brother sin a sin which is not unto death; viz. that appears not obstinate and incurable; he shall ask, i.e. with confidence, as 1 John 5:14. But there is a sin unto death, i.e. which doth not barely deserve death, as all sin doth, nor which argues a person to be probably in a present state of death or unregeneracy, which the sinful ways may do of many that never made profession; but of such as have apostatized from a former specious profession into heresy and debauchery, and continue obstinate therein, against all methods of recovery; that are, as Judges 1:12, even twice dead, & c. I do not say that he shall pray for it; i.e. I do not give that encouragement to pray for such, with that hope and expectation of success, as for others; though he doth not simply forbid praying for them neither.
Related Commentaries of 1 John 5:16
1 John 5:16
16 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.