There is an interesting Halacha related to the idea of אשתו כגופו, that one’s wife is like his own self.
This is learned from the rules in connection with the offerings of the מנחה sacrifice. Generally, only a fistful of the sacrifice is offered on the מזבח. The remainder is a gift to male Kohanim.
The exception is when a Kohein himself needs to offer the קרבן מנחה. In such a case, the fistful known as קמיצה, is offered on the altar, and the remainder is not allowed to be eaten by any Kohein. It, too, is scattered over the ashes burning on the מזבח.
When the wife of a Kohein offers a קרבן מנחה, her sacrifice is also forbidden to be eaten by any Kohein. This is because of her attachment to her husband. Here we say, אשתו כגופו, and it’s as if the Kohein himself offered the sacrifice.
The bond between a Jewish husband and wife is meant to be holy. Their bond becomes so strong that they truly become like one being. This is אשתו בגופו.