Midrash for Taanit 4:11

Moses took || the tables (of the law), and he descended, and the tables carried their own weight and Moses with them; but when they beheld the calf and the dances, the writing fled from off the tables, and they became heavy in his hands, and Moses was not able to carry himself and the tables, and he cast them from his hand, and they were broken beneath the mount, as it is said, "And Moses' anger waxed hot, and he cast the tables out of his hands, and brake them beneath the mount" (Ex. 32:19).