God wanted to create a happy people. Ultimate happiness rests in Him so He made this incredible offer: I will come inside you and give you My joy!
When Jesus comes in, we have a union with Him that is closer than any other union.
We can't give our spouses or our children our joy and our peace. We may tell them what gives us joy or peace, but in order to actually give them the joy we have, we would have to enter them and be a part of them. That is what Jesus promised. We wouldn't just have knowledge of Him; He would reside in us. Jesus' final prayer before He went back to the Father was "...that I myself may be in them" (John 17:26).
Jesus said He had to go away so He could come again--not as a man to walk beside us--but as a Spirit to live within us. The Christ life is Christ re-living His life in us and enabling us to be and to do what in our own strength we never could accomplish.
So He asks that we delight in what He delights in. If His Spirit is one with ours, then we find our joys in what gives God joy.
The key is to obey His commands, and His command is to love others as He loves us. "If you obey my commands, you will remain in my love...I have told you this so that my joy may be in you and that your joy may be complete. My command is this: Love each other as I have loved you" (John 15:10-12).
If we refuse to love--and sometimes we don't find others very lovable--we lose the joy He promises.
Dear Father, what an incredible offer You extend--Your joy for those who love others as You love us! But only by relying on You can we love as You love. Give us grace to always choose to allow You to love through us.
"I am coming to you now, but I say these things while I am still in the world, so that they may have the full measure of my joy within them" (John 17:13).