What are the words and the source of the Shlomo Carlebach song, "Lulei Sorascha (Without Your Torah)"?

I feel that I must have encountered this verse in Tehillim (which I believe is where it comes from), but I was either not thinking about the song whenever I have said this, or else it just didn't stick with me. In any case, I just can't remember or figure out for sure where it is from or what the words are. Surely someone here can help me out. Please?