John 14:11

11 Believe me when I say that I am in the Father and the Father is in me; or at least believe on the evidence of the works themselves.

Believe what I am telling you about this relationship the Father and Son share. You can have confidence in what I am saying, you can trust my words, remember, I AM THE TRUTH!. You can take me at my word. I say what I mean and mean what I say. The Father is in me and I am in Him, there is no separation – only union and oneness that you must believe exists in order to understand who I am.
If for some reason (unbelief, fear) my words are not enough, then look at the evidence of the works themselves. That should be proof enough. It should be obvious that my works back up my words. No one could do what I am doing unless God were working through him/her. The miracles are proof of what I say. My claims are not empty or vain.
What more can I say to convince you? If I was all talk and not walk then I would not blame you for doubting me, but my actions back up my words 100%. I’m giving you ample reason to be able to believe me when I tell you that the Father and I are residing in one another, that we are inseparable, that we are indeed ONE.
I don’t expect you to fully understand this divine mystery just yet, but I do expect you to believe what I say about it. The fact that you request that I show you the Father indicates that not only do you not understand what I’ve said but you also do not trust me to be telling you the truth. If you needed more, then I would have given you more. But what I have shown you and demonstrated to you is enough. It is sufficient.
If you really believed me, your hearts would not be troubled, as they now are.