My prayer is not for them alone. I pray also for those who will believe in me through their message, 21 that all of them may be one, Father, just as you are in me and I am in you. May they also be in us so that the world may believe that you have sent me. 22 I have given them the glory that you gave me, that they may be one as we are one— 23 I in them and you in me—so that they may be brought to complete unity.
How can believers be in Father and Son? Only through the Holy Spirit, there is no other way. And Jesus prayed: just as, you are in me and I am in you may they also be in us.
How can believers be as one? Only through the Holy Spirit, there is no other way:
then make my joy complete by being like-minded, having the same love, being one in spirit and of one mind. Phil2:2 Christians can only be brought to complete unity through the Spirit. And Jesus prayed: That they(believers) may be one AS, AS we are one.
The common link in the verses is the Holy Spirit.