Aristotle's Metaphysics 981a19-20:
οὐ γὰρ ἄνθρωπον ὑγιάζει ὁ ἰατρεύων ἀλλ᾽ ἢ κατὰ συμβεβηκός, ἀλλὰ Καλλίαν ἢ Σωκράτην ... ᾧ συμβέβηκεν ἀνθρώπῳ εἶναι.
For the doctor doesn’t cure a man, except accidentally, but [he cures] Callias or Socrates ... to whom it is happened to be a man.
Why ἀνθρώπῳ as a predicate is dative?
It is notable that in the Latin translation, the equivalent word is accusative:
cui esse hominem accidit