With Ambaṭṭha 1.20.12

1.20.12

Yo kho, ambaṭṭha, tathāgatena yāvatatiyakaṃ sahadhammikaṃ pañhaṃ puṭṭho na byākaroti, etthevassa sattadhā muddhā phalissatī”ti.

If someone fails to answer a legitimate question when asked three times by the Buddha, their head explodes into seven pieces there and then.”