John 13:34-35, 17:23

A new commandment I give to you, that you love one another: just as I have loved you, you also are to love one another. By this all people will know that you are my disciples, if you have love for one another.

I in them and you in me, that they may become perfectly one, so that the world may know that you sent me and loved them even as you loved me. (ESV)