Paṭhamadvayasutta

sn35.92:2.1 Mendicants, suppose someone was to say:

sn35.92:2.2 ‘I’ll deny this duality and describe another duality.’ They’d have no grounds for that claim,

sn35.92:2.3 they’d be stumped by questions, and, in addition, they’d get frustrated.

sn35.92:2.5 Why is that?

sn35.92:2.6 Because they’re out of their element.”