There is a key word in this and it is "given." Those God "gave" His Son in predestination were only the holy apostles. Jesus prays for them, BUT ALSO prays for all those (us) who believe their words.
False doctrines about predestination are that we all are predestined to be saved or damned. NO! To understand the words of the apostles in their writings look for the "key words" and in this case it is "given"
John 17
Jesus Prays for His Disciples (all through this part you see the word "given" to the apostles.
6 “I have manifested Your name to the men whom You have given Me out of the world. They were Yours, You gave them to Me, and they have kept Your word. 7 Now they have known that all things which You have given Me are from You. 8 For I have given to them the words which You have given Me; and they have received them, and have known surely that I came forth from You; and they have believed that You sent Me.
9 “I pray for them. I do not pray for the world but for those whom You have given Me, for they are Yours. 10 And all Mine are Yours, and Yours are Mine, and I am glorified in them. 11 Now I am no longer in the world, but these are in the world, and I come to You. Holy Father, keep through Your name those whom You have given Me, that they may be one as We are. 12 While I was with them in the world, I kept them in Your name. Those whom You gave Me I have kept; and none of them is lost except the son of perdition, that the Scripture might be fulfilled. 13 But now I come to You, and these things I speak in the world, that they may have My joy fulfilled in themselves. 14 I have given them Your word; and the world has hated them because they are not of the world, just as I am not of the world. 15 I do not pray that You should take them out of the world, but that You should keep them from the evil one. 16 They are not of the world, just as I am not of the world. 17 Sanctify them by Your truth. Your word is truth. 18 As You sent Me into the world, I also have sent them into the world. 19 And for their sakes I sanctify Myself, that they also may be sanctified by the truth.
Jesus Prays for All Believers (God has not predestined these, they have free-will) Jesus sets them on a path of glorification which He gives them - His glory.
20 “I do not pray for these alone, but also for those who will believe in Me through their word; 21 that they all may be one, as You, Father, are in Me, and I in You; that they also may be one in Us, that the world may believe that You sent Me. 22 And the glory which You gave Me I have given them, that they may be one just as We are one: 23 I in them, and You in Me; that they may be made perfect in one, and that the world may know that You have sent Me, and have loved them as You have loved Me.
24 “Father, I desire that they also whom You gave Me may be with Me where I am, that they may behold My glory which You have given Me; for You loved Me before the foundation of the world. 25 O righteous Father! The world has not known You, but I have known You; and these have known that You sent Me. 26 And I have declared to them Your name, and will declare it, that the love with which You loved Me may be in them, and I in them.”
V24 is referring to all believers not just the apostles, and comes after where Jesus has talked about those who will believe in Christ who are not apostles.
The word 'ALSO' is pointing to the separate group he had just introduced in v20
24 “Father,
I desire that they also whom You gave Me may be with Me where I am, that they may behold My glory which You have given Me; for You loved Me before the foundation of the world.
And we have a sure word about that pointed out by Christ in John 6 in much of the chapter, he is referring to all who believe not talking about the apostles only.
Referring to any and all who do come, not just apostles.
37
All that the Father gives Me will come to Me, and the one who comes to Me I will by no means cast out.
The ones who come to Christ as believers have all been taught by God.
44 No one can come to Me unless the Father who sent Me draws him; and I will raise him up at the last day.
45 It is written in the prophets, ‘And they shall all be taught by God.’ Therefore everyone who has heard and learned from the Father comes to Me.
God must grant for someone to come to Christ, that is what it means to be given to Christ by God.
If they are not granted this, then they will never believe.
Knowing Christ is by direct revelation from God the Father to a person, by His Spirit, and not by the flesh can anyone know God and Christ. So being saved is entirely dependent on if God has granted you to know the Godhead. Jesus points this out here, that without God granting you to come to Christ you will never believe.
63
It is the Spirit who gives life; the flesh profits nothing. The words that I speak to you are spirit, and
they are life. 64 But there are some of you who do not believe.” For Jesus knew from the beginning who they were who did not believe, and who would betray Him. 65 And He said, “
Therefore I have said to you that no one can come to Me unless it has been granted to him by My Father.”
Then we get more confirming of this here in Luke 10. about who gets to know who Christ is, meaning salvation is by God willing you to know Christ. Only then are you saved, life by the Spirit, not by the flesh (from your own reasoning mind). If you dont know Him, then your not a saved person.
21 In that hour Jesus rejoiced in the Spirit and said, “I thank You, Father, Lord of heaven and earth, that You have hidden these things from
the wise and prudent and revealed them to babes. Even so, Father, for so it seemed good in Your sight. 22 All things have been delivered to Me by My Father, and no one knows who the Son is except the Father, and who the Father is except the Son, and
the one to whom the Son wills to reveal
Him.”