Mūlapariyāya Jātaka (No.245)
The Bodhisatta was once a brahmin teacher of great fame. Among his pupils were five hundred brahmins, versed in the three Vedas, who thought they knew as much as their teacher. The Bodhisatta, aware of this, gave them a riddle to solve: “Time consumes all, even itself, but who can consume the all consumer?” For a whole week they tried to find a solution and then admitted defeat. The Bodhisatta rebuked them, saying that they had holes in their ears but no wisdom. Their pride was quelled, and from that time they honoured their teacher.
The story was told in reference to some monks: to whom the Mūlapariyāya Sutta was taught. The disciples are the same in both cases. J.ii.259‑262.