Of course, oneness in marriage reaches far beyond the physical level.

The original Hebrew word translated as “flesh” refers to much more than a person’s physical or sexual composition. It relates to the whole human existence.

The biblical view of “one flesh” communicates a unity that covers every facet of a couple’s joint lives as husband and wife.

In marriage, two whole lives unite together as one emotionally, intellectually, financially, spiritually, and in every other way. The “two shall become one” in purpose.

They are so close that they function like one person, balancing each other’s strengths and weaknesses so that together they can fulfill their God-given calling.

https://www.gotquestions.org/the-two-shall-become-one-flesh.html