Chava Jātaka (No.309)
The Bodhisatta was once born as an outcaste (caṇḍāla). His wife, being with child, yearned to eat a mango, and he went by night to the king’s garden to try and get one. However, day broke before he could escape and he remained perched in the tree. While he was there, the king came with his chaplain and, sitting on a high seat at the foot of the tree, learnt the Dhamma from the chaplain, who occupied a low seat. The Bodhisatta climbed down from the tree and pointed out to them their error. The king, being very pleased, made him ruler of the city by night and placed round his neck the garland of red flowers which he himself was wearing. Hence the custom of the lords of the city to wear a wreath of red flowers.
The story was related in reference to the Chabbaggiyā monks, who taught the Doctrine to those who sat on a higher seat than they themselves. J.iii.27 ff.