Preached to the monks at Desakā in the Sumbhā country. Supposing the fairest maiden in all the countryside were to dance and sing in public, and a man were told that if he carried a bowl brimful of oil through the crowd he would win the maiden, but that if he spilt one single drop he would lose his head, that man would not turn his attention to anything else or grow slack in his efforts. In the same way should monks cultivate mindfulness relating to the body (S.v.169f).
This sutta seems also to have been called the Janapadakalyāni Sutta. E.g., J.i.393f.