John 17:9

9.I pray for them. Hitherto Christ has brought forward what might procure for the disciples favor with the Father. He now forms the prayer itself, in which he shows that he asks nothing but what is agreeable to the will of the Father, because he pleads with the Father in behalf of those only whom the Father himself willingly loves. He openly declares that he does not pray for the world, because he has no solicitude but about his own flock, which he received from the hand of the Father. But this might be thought to be absurd; for no better rule of prayer can be found than to follow Christ as our Guide and Teacher. Now, we are commanded to pray for all, (Titus 2:8) and Christ himself afterwards prayed indiscriminately for all,

Father, forgive them; for they know not what they do,
(Luke 23:34.)

I reply, the prayers which we offer for all are still limited to the elect of God. We ought to pray that this man, and that man, and every man, may be saved, and thus include the whole human race, because we cannot yet distinguish the elect from the reprobate; and yet, while we desire the coming of the kingdom of God, we likewise pray that God may destroy his enemies.

There is only this difference between the two cases, that we pray for the salvation of all whom we know to have been created after the image of God, and who have the same nature with ourselves; and we leave to the judgment of God those whom he knows to be reprobate. But in the prayer which is here related there was some special reason, which ought not to be produced as an example; for Christ does not now pray from the mere impulse of faith and of love towards men, but, entering into the heavenly sanctuary, he places before his eyes the secret judgments of the Father, which are concealed from us, so long as we walk by faith.

Besides, we learn from these words, that God chooses out of the world those whom he thinks fit to choose to be heirs of life, and that this distinction is not made according to the merit of men, but depends on his mere good-pleasure. For those who think that the cause of election is in men must begin with faith. Now, Christ expressly declares that they who are given to him belong to the Father; and it is certain that they are given so as to believe, and that faith flows from this act of giving. If the origin of faith is this act of giving, and if election comes before it in order and time, what remains but that we acknowledge that those whom God wishes to be saved out of the world are elected by free grace? Now since Christ prays for the elect only, it is necessary for us to believe the doctrine of election, if we wish that he should plead with the Father for our salvation. A grievous injury, therefore, is inflicted on believers by those persons who endeavor to blot out the knowledgeof election from the hearts of believers, because they deprive them of the pleading and intercession of the Son of God. (116) These words serve also to expose the stupidity of those who, under the pretence of election, give themselves up to the indolence, whereas it ought rather to arouse us to earnestness in prayer, as Christ teaches us by his example.