Moses retells the people of their rebellious behavior, the worst of which was, having experienced the revelation of the truth of the Oneness of all, they still turned back to worshiping idols making the golden calf. The Midrash compares this to an about-to-be-bride who is unfaithful beneath the chuppah. As Moses witnessed this, the letters of the ten commandments on the two luchos – the sapphire tablets – separated and flew away into space. We lost them by our selfish desires.