Rashi on Ki Sisa 32:6

English: וישכימו AND THEY ROSE UP EARLY [IN THE MORNING] — Satan made them zealous in order that they might sin, for later on in the forenoon Moshe actually came down from the mountain. לצחק TO PLAY — There is implied in this term besides idolatry also sexual immorality, — as we find the word used in, (Genesis 39:17) “to mock (לצחק) me” where unchastity is meant as is evident from the context — and blood-shed, as it is said, (II Samuel 2:14) “Let the young men arise and play (וישחקו) before me; [and they caught every one his fellow by the head and thrust his sword in his fellows side]”— here, too, Hur was assassinated (Midrash Tanchuma 3:9:20).