In Matthew 19:5 it states:

And said, For this cause shall a man leave father and mother, and
shall cleave to his wife: and they twain shall be one flesh?

Cleave is an interesting verb, or word, that the Lord decides to use to describe the importance of leaving your past relationships and focusing on your marriage relationship. Of course, the Lord didn’t mean we don’t continue to have good and healthy relationships with our parents, and other important people in our lives, but He wants us to make our marriage relationship the number one and highest priority relationship.

Synonyms for cleave are: Slice, chop, cut, slash, smite and hew. Isn’t that interesting? The key to understanding this verse is understanding the Hebrew definition which is to cut a covenant with God. This goes back to the days of animal sacrifices where the animal was divided or cleaved into two pieces; one piece representing the Lord, the other, you. Hence, a covenant is cut between God and ourselves.

Therefore, the verse is saying we need to have a covenant relationship with our spouse, preferably in the temple, so that by cutting this covenant we are really binding ourselves one to another.

The world does not understand this concept of pure devotion and promise toward one another.  As members of the church, we understand that as,

“spirit sons and daughters [we] knew and worshipped God as [our] Eternal Father and accepted His plan by which His children could obtain a physical body and gain earthly experience to progress toward perfection and ultimately realize their divine destiny as heirs of eternal life.  The divine plan of happiness enables family relationships to be perpetuated beyond the grave.  Sacred ordinances and covenants available in holy temples make it possible for individuals to return to the presence of God and for families to be united eternally.”

(from The Family: A Proclamation to the World)