A Discourse at Sedaka
Thus have I heard — At one time the Blessed One was dwelling in Sumbha at a market town of Sumbha named Sedaka. Then the Blessed One addressed the monks: “At one time, monks, a bamboo acrobat set up a bamboo pole and said to his apprentice “frying-pan:” ‘Dear frying-pan,¹ having climbed the bamboo pole stand on my shoulders.’ Having replied, ‘Very well. teacher,’ monks, frying-pan the apprentice climbed the pole and stood on the teacher’s shoulders.² Then, monks, the bamboo acrobat said to the apprentice frying-pan: ‘Dear frying-pan, you protect me, and I will protect you. Thus  guarding and looking after each other we will show our skill, earn our reward, and descend safely from the bamboo pole.’
When this was said, monks, frying-pan the acrobat’s apprentice said: “No, teacher, it should not be like this. You, teacher, protect yourself, I will protect myself, Thus we will each guard and protect ourselves, show our skill, earn our reward, and descend safely from the bamboo pole.”
“That method, monks, said by frying-pan the acrobat’s apprentice to the teacher should be followed to protect oneself with mindfulness, and to protect others with mindfulness.
“And how, monks, does one, by protecting oneself, protect others? By practising, developing, and making much of the four foundations of mindfulness, thus monks, by protecting oneself, one protects others.
“And how, monks, does one protect others by protecting oneself? By patience, harmlessness, loving-kindness, and compassion (anudayatāya) — thus, monks, by protecting others, one protects oneself.
“Thinking ‘I will protect myself,’ monks, the foundations of mindfulness should be practised; Thinking, ‘I will protect others’ the foundations of mindfulness should be practised. By protecting oneself, monks, one protects others.”
1. The apprentice may have been male although the gender of the word for frying-pan is female.
2. The Commentary says that the trick was for the acrobat to balance the pole on his forehead and for the apprentice to climb the pole. The text suggests that they both climbed the pole and the apprentice stood on the teacher’s shoulders.