Before Moses, divorce was already a wrong choice.
He (Jesus) said to them, “Because of your hardness of heart Moses permitted you to divorce your wives; but from the beginning it has not been this way.”
New American Standard Bible: 1995 Update (La Habra, CA: The Lockman Foundation, 1995), Mt 19:8.
Why was divorce allowed in the OT? This was a question that Jesus turned on the Jewish leaders in the Gospel of Matthew chapter 19 when they asked Him if is is lawful for a man to divorce his wife for any reason. Jesus here reinforces the idea that divorce was not an option from the beginning since from the beginning a husband and wife are one flesh when previously they were two. Moses allowed it due to the “hardness of their hearts.”
Prior to this, the covenant was preserved as any vow or oath stood, and not as a contract. Malachi warns against “dealing treacherously with the wife of your youth” (Malachi 2:14). Following these words in Malachi, the prophet continues speak on behalf of God. God’s position on divorce is very clear, “he hates the putting away [divorce]” (v. 16) said Malachi.
Malachi, like Jesus, had to remind Judah of God’s original plan in marriage, “And did not he make one?” (v. 15). Man and woman were to leave their fathers and mothers to become “one flesh” (Gen. 2:24). In creating man and woman God was still left with the “residue of the spirit” (2:15). Why did God make them one? For the fruit of godly offspring. Has not God been ONE Father to us all? Has not ONE God created us? (Malachi 2:10). He has not adulterated Himself to any and His offspring are to be ONE.
Now, concerning the ONE thing, let’s explore the unity of the flesh of Adam and Eve. Adam, we know, was created from the dust of the ground. Eve was formed from the “side” of Adam. The Hebrew for “side” sela can be interpreted as something from his inside, as in a “rib,” but more than that, his “side.” The word is used for hillside, mountainside, and extension of a building. It’s a architectural term meaning to split, as in section. It could easily be seen as Adam being cut, or sectioned, (in half) and from the two halves came a man and woman. And the two were one “flesh.” The Hebrew word for “flesh” is bassar. It is a word can not only apply to human and animal flesh, but with sacrificial ordinances and covenant obligations (Lev 7:17).
And Adam said:
"This is now bone of my bones
And flesh of my flesh;
She shall be called Woman (Heb. Ishaah),
Because she was taken out of Man."(Heb. Ish).
The New King James Version (Nashville: Thomas Nelson, 1982), Ge 2:23.
Why does God hate divorce so? Because it violates His original and intentional plan for marriage (Gen. 2:24; Mt. 19:4-6) and brings untold hardship on those involved, destroying both the family and society. Jesus is speaking to a Jewish audience who understood marriage would be first engaged then consummated. If the exception clause exists, it is to ensure that virginity is the emphasis when selecting a spouse. Putting someone away for porneia ensured that if one is discovered to have not been a virgin at marriage, then the consummation must not be allowed. Jesus emphasized it when He said, “Anyone who marries a divorced woman/man is guilty of adultery.” To harmonize the Old Testament Mosaic exception, we have to find agreement with this since Deut. 22:22; Lev. 20:10-18 reveal to us that adultery is punishable by death.