Sinning for Good

 Avoda Zara (04b) The Israelites made the golden calf only in order to place a good argument in the mouth of the penitents, as it is said, O that they had such a heart as this alway, to fear Me and keep all My commandments etc.This last statement accords with what R. Johanan said in the name of R. Simeon b. Yohai: David was not the kind of man to do that act, nor was Israel the kind of people to do that act. David was not the kind of man to do that act, as it is written, My heart is slain within me; nor were the Israelites the kind of people to commit that act, for it is said, O that they had such a heart as this alway etc. Why, then, did they act thus? God predestined it so in order to teach thee that if an individual hath sinned and hesitates about the effect of repentance he could be referred to the individual David, and if a community commit a sin they should be told: Go to the community.