At Sedaka (The Beauty Queen)
Sedaka Sutta (2)  (SN 47:20)

I have heard that on one occasion the Blessed One was staying among the Sumbhas. Now there is a Sumbhan town named Sedaka. There the Blessed One addressed the monks, “Monks!”

“Yes, lord,” the monks responded to him.

The Blessed One said, “Suppose, monks, that a large crowd of people were to come thronging together, saying, ‘The beauty queen! The beauty queen!’ And suppose that the beauty queen were highly accomplished at singing & dancing, so that an even greater crowd would come thronging, saying, ‘The beauty queen is singing! The beauty queen is dancing!’ Then a man would come along, desiring life & shrinking from death, desiring pleasure & abhorring pain. They would say to him, ‘Now look here, mister. You must take this bowl filled to the brim with oil and carry it on your head in between the great crowd & the beauty queen. A man with a raised sword will follow right behind you, and wherever you spill even a drop of oil, right there will he cut off your head.’ Now what do you think, monks? Would that man, not paying attention to the bowl of oil, let himself get distracted outside?”

“No, lord.”

“I have given you this parable to convey a meaning. The meaning is this: The bowl filled to the brim with oil stands for mindfulness immersed in the body. Thus you should train yourselves: ‘We will develop mindfulness immersed in the body. We will pursue it, hand it the reins, take it as a basis, steady it, consolidate it, and undertake it well.’ That is how you should train yourselves.”

See also: MN 119; SN 35:115; SN 35:206