It was Jesus' prayer for us in the garden the night before he was crucified. That we would be one as he and the father are one.
Joh 17:11 -
I will remain in the world no longer, but they are still in the world, and I am coming to you. Holy Father, protect them by the power of your name--the name you gave me--so that they may be one as we are one.
Joh 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.
Joh 17:22 -
I have given them the glory that you gave me, that they may be one as we are one: