Upvote:2
I have searched the writings of Bernard of Clairvaux, and was unable to find that exact quote. It's possible that your quote was a paraphrase of the original.
I do know that the closing sentence of "On the Love of God" is "Those who love God are one Spirit with Him." This seems to be close to the meaning, if not the actual words.
Often in history we don't know everything with absolute certainty, and the best we have is an incomplete picture based on what we know.