Sforno on Genesis 2:24/ספורנו על בראשית ב׳:כ״ד

1על כן, seeing that on this first occasion G’d had aimed to make Adam’s wife as much part of him as possible, so that he even used Adam’s personal body as Chavah’s basic skeleton,

2יעזוב איש את אביו ואת אמו ודבק באשתו, it is appropriate that a man leave the home of his parents in order to acquire a wife who is compatible with him, and who is a suitable mate for him to live with on a permanent basis. The Torah teaches here also that the expression דיבוק, “cleaving,” being in a state of true union, is not possible between two people who are not alike in their common purpose in life. Parents and children do not have the same tasks and challenges. Man and his wife do have to master the same challenges, hence the word “union” can be applied to their union, whereas the same word would be inappropriate for describing the relationship between father and son, or mother and son. By living together they will become of one mind on how to deal with their lives’ challenges.

3 והיו לבשר אחד, they are to work together in such close union as if there were in fact only one of them. (This had been the idea behind creating man as both male and female in the first place.)