Moses, in Genesis, documents the institution of marriage:

Then God said, “Let Us make man in Our image, after Our likeness, to rule over the fish of the sea and the birds of the air, over the livestock, and over all the earth itself and every creature that crawls upon it.”
Then the LORD God formed man from the dust of the ground and breathed the breath of life into his nostrils, and the man became a living being.
The LORD God also said, “It is not good for the man to be alone. I will make for him a suitable helper.”

So the LORD God caused the man to fall into a deep sleep, and while he slept, He took one of the man’s ribs and closed up the area with flesh. And from the rib that the LORD God had taken from the man, He made a woman and brought her to him. And the man said:

“This is now bone of my bones
     and flesh of my flesh;
she shall be called ‘woman,’
     for out of man she was taken.”

For this reason a man will leave his father and mother and be united to his wife, and they will become one flesh.

Gen 1 & 2

But as history unfolds after the fall, the text in the Torah becomes almost insensitive to the practice of polygamy and the taking of concubines. The breakdown of the institution of the marriage union began at the fall in Genesis 3 and spread quickly.

Legislation that allowed for divorce entered society. Jesus attributed this degradation to a "hardness of heart".

Then some Pharisees came and tested Him by asking, “Is it lawful for a man to divorce his wife for any reason?”

Jesus answered, “Have you not read that from the beginning the Creator ‘made them male and female,’ and said, ‘For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh’? So they are no longer two, but one flesh. Therefore what God has joined together, let man not separate.”

“Why then,” they asked, “did Moses order a man to give his wife a certificate of divorce and send her away?”

Jesus replied, “Moses permitted you to divorce your wives because of your hardness of heart; but it was not this way from the beginning.

Matt 19:3-8

The Bible doesn't hide the ugly record of deviating from the Genesis ideal. We can see the results of this as early on as Abraham:

Now Abram’s wife Sarai had borne him no children, but she had an Egyptian maidservant named Hagar. So Sarai said to Abram, “Look now, the LORD has prevented me from bearing children. Please go to my maidservant; perhaps I can build a family by her.”

And Abram listened to the voice of Sarai. So after he had lived in Canaan for ten years, his wife Sarai took her Egyptian maidservant Hagar and gave her to Abram to be his wife. And he slept with Hagar, and she conceived. But when Hagar realized that she was pregnant, she began to despise her mistress.

Then Sarai said to Abram, “May the wrong done to me be upon you! I delivered my servant into your arms, and ever since she saw that she was pregnant, she has treated me with contempt. May the LORD judge between you and me.”

“Here,” said Abram, “your servant is in your hands. Do whatever you want with her.” Then Sarai treated Hagar so harshly that she fled from her.

Gen 16:1-6

This deviation, resulted in rivalry and conflict between Isaac and Ishmael that lasts to this day.

We can also see the steady creep of polygamy during the reign of the kings.

  • Saul had one wife and a concubine.
  • David had at lease 8 wives and untold concubines. 
  • Solomon had 700 wives and 300 concubines.

The consequences of disregarding the ideal are apparent. "If you read the stories about the characters referenced above, you’ll quickly find that polygamy was an unmitigated sociological disaster that created heartbreak and sowed familial discord."

See: How Should We Respond to Old Testament Polygamy?