大般涅槃經集解 18.203

18.203

案道生曰：無明為眾結之首也。僧亮曰：我見是眾結之首，故云以頭觸之也。僧宗曰：圓解以正信為首，邪心以不信為頭。信為不信所侵，如二首相觸之。

Daosheng states: Ignorance is the head of all fetters. Sengliang states: The view of self is the head of all fetters, hence it says he struck him with his head. Sengzong states: Complete understanding has correct faith as its head; the deviant mind has unfaith as its head. Faith being invaded by unfaith is like two heads striking each other.