It's

John 14:20 

On that day you will realize that I am in my Father, and you are in me, and I am in you.

John 17:23 

I in them and you in me—so that they may be brought to complete unity. Then the world will know that you sent me and have loved them even as you have loved me.

John 17:21 

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.

Not like he's saying anything new.