Himself-Him-Self | Commonly Confused Words

Himself

/ɪm'self/

Used to refer to a man, boy, or male animal when the subject and object of the verb are the same person or animal

He was beside himself.Sikes himself is sure to show up soon!"And he had been thrilled in spite of himself.

This word has no antonyms

/hɪmˈsɛlf/

Refers to a male person and emphasizes he is doing something alone or by himself.

Himself is a single word and used as a pronoun.
Him self is an incorrect split of himself and generally not used in modern English writing.
Himself typically refers back to another male person mentioned earlier in the sentence.
Remember that himself is a reflexive pronoun used for emphasis or to indicate the subject's involvement.
If you write him self, it will be considered a typographical error unless there's a specific, rare context that warrants it.