Three things are evident from this verse.
1. That Christ did not pray for any reprobates, not for any that were and should die unbelievers: he prayed before for those who actually did believe; he prays here for them that should believe; but we never read that he prayed for any others. Now whether he laid down his life for those for whom he would not pray, lies upon them to consider, who are so confident that he died for all and every man.
2. That by persons given to Christ, cannot be understood believers as such; for Christ here prays for those that were not actual believers, but should believe.
3. That faith cometh by hearing; Christ here prays for those that should believe through their word, that is, the apostles preaching the gospel.