himself; he himself
Reflexive pronoun emphasizing the male subject; used when the subject performs an action on or by himself, or to stress that it is he and not someone else.
He himself admitted it.
He blamed himself.
A more general reflexive pronoun meaning 'oneself'; can be used for any person, while 彼自身 is specifically male third person.
Compound of 彼 (かれ, 'he') + 自身 (じしん, 'self'). The reading かれじしん is a straightforward combination of the two components.