Choose the statement with best punctuation: He is to tell the truth a fool?

He is to tell the truth a fool.

He is, to tell the truth, a fool.

He is to tell the truth; a fool.

He is: to tell the truth, a fool.

He is, to tell the truth, a fool.

This sentence uses commas to set off the parenthetical phrase "to tell the truth".

This making it clear and grammatically correct.