'L'amor che move il sole e l'altre stelle'?
It's a bit of the very last verse from Paradiso-Dante's Paradise.
'My will and my desire were turned by love, the love that moves the sun and the other stars.' 

Dante was trying to explain faith, I think, as an overpowering love, and maybe it's blasphemous, but that's how I think of the way that I love you. You came into my life and suddenly I had one truth to hold on to-that I loved you, and you loved me.

            Jace to Clary 
            The Mortal Instruments book 4
            City of Fallen Angels