The Sin unto Death.
St. John appears to speak of some one sin as standing apart from all others, as a sin unto death a sin so fatal, so entirely beyond the possibility of pardon, that Christians should even refrain from making petitions to God on behalf of one who had committed this sin. A little consideration, however, may lead us to conclude that such was not precisely the meaning which was in St. John's mind when he wrote. The Apostle is speaking of the power of a Christian's prayers. He shows it to be an immediate consequence of our faith in Jesus Christ as the Son of God that we should offer up our prayers in full confidence that those prayers will be heard, and that they will be answered, provided only that the petition is in accordance with God's holy will. He then goes on to show that a Christian may obtain forgiveness for his brother by intercession, provided that the sin for which he prays has not been a deadly sin, a sin unto death. St. John is evidently anxious that his doctrine of intercession should not be abused, and therefore he limits his doctrine by saying that there is a kind of sin for which he cannot venture to encourage Christians to pray with the hope that the sin will be pardoned. St. John is not laying down a rule as to what sins can be pardoned and what not, but as to what sins form a fair and proper subject for Christian intercession. Let us learn from the subject that sin is certainly a more deadly thing than many men suppose, and that there is danger lest those whom Christ has redeemed should fall away from grace and never rise again. Therefore let him who thinks that he stands take heed lest he fall.
Harvey Goodwin, Parish Sermons,vol. iii., p. 383.
References: 1 John 5:16. H. W. Beecher, Christian World Pulpit,vol. ix., p. 132. 1 John 5:16; 1 John 5:17. Homiletic Magazine,vol. vi., p. 183. 1 John 5:17. Ibid.,vol. vii., p. 60; Clergyman's Magazine,vol. ii., p. 264. 1 John 5:18. Expositor,1st series, vol. vii., p. 210.