The Marriage between God and the Hebrews

In the Canaanite polytheism, the head of the pantheon was El, with his consort Asherah. El had 70 sons, and each (or some?) was connected to a specific people. Yahweh was the god associated with the people of Israel and Judah.

That connection was very much analogous to a marriage between the god and the nation (at least for the Hebrews), and it may be that Old Testament ideas about marriage were derived from he relationship between God and Israel/Judah, though it might just as easily be that the relationship derived from ideas about marriage.

God was very much the husband, so he set the rules, and he was free to have more than one wife; Israel and Judah specifically. On the other hand, if the people of Israel or Judah started to worship other gods, this was analogous to adultery or even prostitution, and would make God very angry.

Ezekeil sums this up nicely:

Ezekiel 16:6 “‘Then I passed by and saw you kicking about in your blood, and as you lay there in your blood I said to you, “Live!”[a] 7 I made you grow like a plant of the field. You grew and developed and entered puberty. Your breasts had formed and your hair had grown, yet you were stark naked.
8 “‘Later I passed by, and when I looked at you and saw that you were old enough for love, I spread the corner of my garment over you and covered your naked body. I gave you my solemn oath and entered into a covenant with you, declares the Sovereign Lord, and you became mine.
...
15 “‘But you trusted in your beauty and used your fame to become a prostitute. You lavished your favors on anyone who passed by and your beauty became his. 16 You took some of your garments to make gaudy high places, where you carried on your prostitution. You went to him, and he possessed your beauty.[b] 17 You also took the fine jewelry I gave you, the jewelry made of my gold and silver, and you made for yourself male idols and engaged in prostitution with them.

The "high places" would be temples to other gods, built on hilltops, whilst the "male idols" where obviously statues of other gods. Jeremiah mentions also "under every green tree", a reference to the worship of Asherah, El's consort, and her sacred trees.

Jeremiah 3:1 “If[a] a man divorces his wife
    and she goes from him
and becomes another man's wife,
    will he return to her?
Would not that land be greatly polluted?
You have played the whore with many lovers;
    and would you return to me?
declares the Lord.
...
6  The Lord said to me in the days of King Josiah: “Have you seen what she did, that faithless one, Israel, how she went up on every high hill and under every green tree, and there played the whore? 7 And I thought, ‘After she has done all this she will return to me,’ but she did not return, and her treacherous sister Judah saw it. 8 She saw that for all the adulteries of that faithless one, Israel, I had sent her away with a decree of divorce. Yet her treacherous sister Judah did not fear, but she too went and played the whore. 9 Because she took her whoredom lightly, she polluted the land, committing adultery with stone and tree. 10 Yet for all this her treacherous sister Judah did not return to me with her whole heart, but in pretense, declares the Lord.”

Jeremiah was around about a century after the fall of Israel, until around the time Judah was captured by Babylon. Israel, then, is "that faithless one", sent away with a decree of divorce. Jeremiah is then warning the same will happen to her sister, Judah.

Contrast to Isaiah, written around the time Israel fell:

Isaiah 50:1 Thus says the Lord:
“Where is your mother's certificate of divorce,
    with which I sent her away?
Or which of my creditors is it
    to whom I have sold you?
Behold, for your iniquities you were sold,
    and for your transgressions your mother was sent away.

This seems to be saying that there was no certificate of divorce, but that Israel has merely been sent away. The next couple of chapters are then expressing confidence that God will promptly restore Israel, just as soon as the people worship him alone. Clearly when Isaiah was writing, they were hopeful Israel would re-gain independence, so did not consider it a divorce. A century later, the situation had changed, and there was no chance for Israel, and it seemed likely Judah was next, so Jeremiah believed that Israel had been divorced, and that Judah was heading that way, unless the people changed their ways.

The text in Hosea 2 also dates from around the fall of Israel, and it is clear that the god the people were worshiping instead of Yahweh was Ba'al.

Hosea 2:2 “Plead with your mother, plead—
    for she is not my wife,
    and I am not her husband—
that she put away her whoring from her face,
    and her adultery from between her breasts;
3 lest I strip her naked
    and make her as in the day she was born,
and make her like a wilderness,
    and make her like a parched land,
    and kill her with thirst.
...
The Lord's Mercy on Israel
14 “Therefore, behold, I will allure her,
    and bring her into the wilderness,
    and speak tenderly to her.
15 And there I will give her her vineyards
    and make the Valley of Achor[e] a door of hope.
And there she shall answer as in the days of her youth,
    as at the time when she came out of the land of Egypt.

16 “And in that day, declares the Lord, you will call me ‘My Husband,’ and no longer will you call me ‘My Baal.’ 17 For I will remove the names of the Baals from her mouth, and they shall be remembered by name no more. 18 And I will make for them a covenant on that day with the beasts of the field, the birds of the heavens, and the creeping things of the ground. And I will abolish[f] the bow, the sword, and war from the land, and I will make you lie down in safety. 19 And I will betroth you to me forever. I will betroth you to me in righteousness and in justice, in steadfast love and in mercy. 20 I will betroth you to me in faithfulness. And you shall know the Lord.

An important consequence of all this is that adultery and prostitution become symbolically linked to blasphemy. Furthermore, controlling female sexuality is linked to controlling the worship of other gods. No wonder the Bible is so big on that stuff!