Genesis 24:2-3 - Why did Abraham have his servant put his hand under his thigh and swear?

Apparently, this was a way of having someone take an oath when the situation being sworn was very serious.  Putting the hand under the thigh was a euphemism, a nice way of saying that the servant put his hand on Abraham's "procreative organ".  While there is speculation as to what such an act was supposed to signify in an oath it is clear that doing something like this made the oath a very serious matter.

Genesis 32:24-30 - Who was the man that Jacob wrestled with?

The man that Jacob wrestled with was God.  Before Jesus came as a baby, a real human being, there were situations like this where Yahweh, probably Jesus, takes on the form of a human being, a man, to interact with another person, in this case to wrestle with Jacob. As you read through this passage it is clear that Jacob somehow knew this was God because he says that he had just seen God face to face and lived.  Jacob asked this man to bless him because he knew this must be God or some being sent from God.

Genesis 30:4-5 - Did Jacob also get married to the servant girls of Leah and Rachel because they are called his wives?

When Jacob got married to Rachel and Leah each of them was given a woman to be her personal servant.  In Genesis 30:4-5 Rachel chooses to give her servant girl, Bilhah, as a wife to Jacob so that Rachel could bear children through her servant girl since Rachel was childless.  The Hebrew word for "wife" here is the same word as the one that is used when Leah and Rachel get married to Jacob in a marriage celebration.  So, how is the servant girl, Bilhah, called a wife just like Rachel, her mistress, when Bilhah was never "married" to Jacob in an official, cultural ceremony?

The Hebrew word that is translated "wife" in Genesis 30:5 has the general meaning of woman or womanhood.  It gets the meaning of "wife" from its use in a particular context.  So, when Rachel and Leah got married to Jacob they were called wives not only because they were married but because of that marriage they would have sexual relations with their husband Jacob.  When Bilhah is given to Jacob as a "wife" even though there is no marriage ceremony or celebration she is being given as a sexual partner for the purpose of producing offspring and this makes her a wife to Jacob.

Genesis 28:11 - Why did Jacob put a stone under his head to sleep?

Unlike today when we have hotels and airbnb in which to stay when we travel Jacob had nothing like that.  He simply has to find a place to lay down out in the open field and sleep.  He also doesn't carry a pillow with him.  So he has to use what is available where he chooses to spend the night.  In this case he simply chooses a stone to put under his head as a pillow.

Genesis 27:46 - Why were Esau's wives a source of grief to Rebekah?

The Canaanite or Hittite wives that Esau married would have brought their heathen practices of worshipping their false gods.  As Isaac's wife, Rebekah, would have been taught the ways of Yahweh from both Isaac and perhaps even Abraham she would have been a committed follower of Yahweh.  Esau's marriage of these two Hittite women showed his total disregard for the worship of Yahweh.  This would have caused grief to Rebekah as she watched her oldest son completely reject Yahweh and probably even join in with the worship practices of his two wives.

Genesis 19:26 - Why did Lot's wife become a pillar of salt?

The short quick answer is that Lot's wife looked back at Sodom, which she was told not to do, and became a pillar of salt. The follow-up question is, why would looking back turn her into a pillar of salt?  

We need to start with the attitude of Lot, and likely his wife, in this crisis.  Far from being grateful for God's mercy in coming to rescue him Lot is hesitant to leave at the angel's insistence.  The angels literally have to drag him and his family out of Sodom.  They were about to lose everything they had worked for and the fact of that loss seemed to pull Lot and his wife back to Sodom despite the impending judgment. Once they were out of the city Lot complained about where the angels were sending them making the angels agree to Lot's request. So, this is really the setting in which Lot's wife looks back.

Lot's wife look behind her was more than a glance.  For years I thought that all she did was do a quick glance over her shoulder that caused her to turn into a pillar of salt on the spot.  But that is not what happened.  One commentary said that the text implies that she went behind her husband and looked backwards.  She was so conflicted about leaving Sodom and all her earthly belongings that she takes a deliberate action to go behind her husband and turn around to look.  The implication is that this hesitation caused her to get caught in the firestorm of falling burning material and is killed where she stood.  Her body eventually becomes encrusted with salt which makes her body into a pillar of salt.

Genesis 47:29-31,49:29-32 - Why did Jacob want to be buried in Canaan with his fathers?

I believe this was an act of faith.  Jacob believes that though his whole family has moved down to Egypt to sojourn there God will bring them back to the land of Canaan, the land that God Himself had promised to give to Jacob and his offspring.  If Jacob truly believes this he will not want to be buried in Egypt but back in Canaan.  In Hebrews 11:21 it says that by faith Jacob worshipped leaning on his staff.  He did this in Genesis 47:31 after Joseph, his son, swears to Jacob to bury him in the family tomb in Canaan.  Jacob, in faith, worships God who has been his shepherd his whole life and who he knows will bring his offspring back to Canaan one day to where he is buried.  

Genesis 12:8 - Why did Abram have to build an altar at Bethel?

Nowhere does it say that Abram had to build an altar at Bethel. In verse 7 God speaks to Abram and promises to give the land in which Abram is dwelling to him.  In response Abram builds an altar to the Lord. Then, in verse 8 Abram moves from where he is dwelling in verse 7 to the place between Ai and Bethel. Then, Abram decides, on his own, to build the alter at Bethel and call on the Lord.  The Bible doesn't tell us any more about this event as to why Abram was calling on the Lord.

It is useful to note that act of setting up an altar an calling on the name of the Lord is not an insignificant event. Altars like this open portals into the heavenly realm and created places where heaven and earth meet.  Two generations later, in Genesis 28:10-21, Abram's grandson Jacob, comes to the same place, spends the night, and has a dream of an open heaven with a ladder from earth to heaven with angels descending and ascending and the Lord renewing the covenant promise to Jacob to be with him and give him the land of Canaan.

Genesis 15:7-21 - What is the meaning of the animals being cut in half?

In Genesis 15:8-10 God tells Abram to bring certain animals which were to be of a certain age.  Abram brings the animals, slaughters them, cuts them in half and lays out the halves facing each other. This was the conclusion of an ancient custom in that part of the world to finalize a covenant.  God had just told Abram that he through his offspring would inherit the land on which he was living as a stranger at that time.  Abram wants to know what assurances God will give him that the promise God made will happen.

God chooses to use the culturally accepted way of sealing a covenant so Abram would have confidence in the promise God had made.  This is where God asks Abram to bring the animals, Abram, knowing the customs of the their culture understands what God is doing and slaughters and cuts the animals in half and lays out the pieces.  The custom of the sealing the covenant was that the two parties making the covenant would walk between the halves of the dead animals and in doing so covenanting that if either party broke the covenant they would become like the dead animals.  You pledged your life in theses covenants.

In this scene there is one difference.  Only God passes through the pieces and not Abram because only God could bring about the fulfilling of the promise of inheritance He had just made to Abram.  Abram had no part to play in the fulfillment of this covenant.