Why are there so many examples of polygamy in the Bible?

What does God think about polygamy - having more than one wife or husband?

The following excerpt from an article in Nelson's Illustrated Bible Dictionary accurately presents the history and the Bible's teaching:

"The practice of having several spouses, especially wives, at one time. Polygamy includes polygyny (marriage to more than one woman) and polyandry (marriage to more than one man). The term polygamy is more often used, however, as a synonym for polygyny, which was common throughout the ancient world.

"According to the custom of the times, Abraham took Hagar, the Egyptian maidservant of his wife Sarah, to be his wife when Sarah was unable to bear a child (Gen 16:1-4 [1] Now Sarai Abram's wife bare him no children: and she had an handmaid, an Egyptian, whose name was Hagar.
[2] And Sarai said unto Abram, Behold now, the LORD hath restrained me from bearing: I pray thee, go in unto my maid; it may be that I may obtain children by her. And Abram hearkened to the voice of Sarai.
[3] And Sarai Abram's wife took Hagar her maid the Egyptian, after Abram had dwelt ten years in the land of Canaan, and gave her to her husband Abram to be his wife.
[4] And he went in unto Hagar, and she conceived: and when she saw that she had conceived, her mistress was despised in her eyes.

See All...). Abraham's son, Isaac, had only one wife; but Abraham's grandson, Jacob, took two wives (Leah and Rachel) and two concubines, Zilpah and Bilhah (Gen 29:15-30 [15] And Laban said unto Jacob, Because thou art my brother, shouldest thou therefore serve me for nought? tell me, what shall thy wages be?
[16] And Laban had two daughters: the name of the elder was Leah, and the name of the younger was Rachel.
[17] Leah was tender eyed; but Rachel was beautiful and well favoured.
[18] And Jacob loved Rachel; and said, I will serve thee seven years for Rachel thy younger daughter.
[19] And Laban said, It is better that I give her to thee, than that I should give her to another man: abide with me.
[20] And Jacob served seven years for Rachel; and they seemed unto him but a few days, for the love he had to her.
[21] And Jacob said unto Laban, Give me my wife, for my days are fulfilled, that I may go in unto her.
[22] And Laban gathered together all the men of the place, and made a feast.
[23] And it came to pass in the evening, that he took Leah his daughter, and brought her to him; and he went in unto her.
[24] And Laban gave unto his daughter Leah Zilpah his maid for an handmaid.
[25] And it came to pass, that in the morning, behold, it was Leah: and he said to Laban, What is this thou hast done unto me? did not I serve with thee for Rachel? wherefore then hast thou beguiled me?
[26] And Laban said, It must not be so done in our country, to give the younger before the firstborn.
[27] Fulfil her week, and we will give thee this also for the service which thou shalt serve with me yet seven other years.
[28] And Jacob did so, and fulfilled her week: and he gave him Rachel his daughter to wife also.
[29] And Laban gave to Rachel his daughter Bilhah his handmaid to be her maid.
[30] And he went in also unto Rachel, and he loved also Rachel more than Leah, and served with him yet seven other years.

See All...:13).

"The Bible presents monogamy as the divine ideal. The Creator made marriage as a union between one man and one woman (Gen 2:18-24 [18] And the LORD God said, It is not good that the man should be alone; I will make him an help meet for him.
[19] And out of the ground the LORD God formed every beast of the field, and every fowl of the air; and brought them unto Adam to see what he would call them: and whatsoever Adam called every living creature, that was the name thereof.
[20] And Adam gave names to all cattle, and to the fowl of the air, and to every beast of the field; but for Adam there was not found an help meet for him.
[21] And the LORD God caused a deep sleep to fall upon Adam, and he slept: and he took one of his ribs, and closed up the flesh instead thereof;
[22] And the rib, which the LORD God had taken from man, made he a woman, and brought her unto the man.
[23] And Adam said, This is now bone of my bones, and flesh of my flesh: she shall be called Woman, because she was taken out of Man.
[24] Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh.

See All...; Matt 19:4-6 [4] And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female,
[5] 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?
[6] Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder.

See All...; 1 Cor 6:16What? know ye not that he which is joined to an harlot is one body? for two, saith he, shall be one flesh.
See All...)...

"After the time of Moses, polygamy continued to be practiced, especially by wealthy individuals, such as Gideon, Elkanah, Saul, and David (1 Sam 1:2And he had two wives; the name of the one was Hannah, and the name of the other Peninnah: and Peninnah had children, but Hannah had no children.
See All...; 2 Sam 5:13And David took him more concubines and wives out of Jerusalem, after he was come from Hebron: and there were yet sons and daughters born to David.
See All...; 1 Kin. 11:3). But the most famous polygamist in the Bible was King Solomon: 'And he had seven hundred wives, princesses, and three hundred concubines; and his wives turned away his heart' (1 Kin. 11:3). The criticism of polygamy expressed in (Deuteronomy 17:17Neither shall he multiply wives to himself, that his heart turn not away: neither shall he greatly multiply to himself silver and gold.
See All...), therefore, is not surprising: the ideal king to whom Israel's obedience can be rightly given shall not 'multiply wives for himself, lest his heart turn away'" (1986, "Polygamy").

Scripture shows that it was God's intention for man to be monogamous. When a group of religious leaders approached Jesus on the related subject of divorce, Jesus pointed them back to the creation (Matthew 19:4-6 [4] And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female,
[5] 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?
[6] Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder.

See All...). God had created only one wife for Adam, and it was clearly stated that the two of them were to become one. Later, Paul specified to Timothy that Church leaders must have only one wife (1 Timothy 3:2A bishop then must be blameless, the husband of one wife, vigilant, sober, of good behaviour, given to hospitality, apt to teach;
See All..., 12).