Gen. 20:9-13 Abimelech reproves Abraham 

Gen. 20:9 "Then Abimelech called Abraham, and said unto him, What hast thou done unto us? and what have I offended thee, that thou hast brought on me and on my kingdom a great sin? thou hast done deeds unto me that ought not to be done. 10 And Abimelech said unto Abraham, What sawest thou, that thou hast done this thing? 11 And Abraham said, Because I thought, Surely the fear of God is not in this place; and they will slay me for my wife's sake. 12 And yet indeed she is my sister; she is the daughter of my father, but not the daughter of my mother; and she became my wife. 13 And it came to pass, when God caused me to wander from my father's house, that I said unto her, This is thy kindness which thou shalt show unto me; at every place whither we shall come, say of me, He is my brother." 

Abimelech acknowledged his own sin in taking Sarah, even, calling it a "great sin."  Yet, Abimelech also knew that this whole episode would not have taken place if Abraham and Sarah had been forthcoming concerning their relationship.  He had every right to question the actions of Abraham and to admonish him for doing what he did.  Abraham and Sarah through their deceitfulness brought Abimelech and Gerar into a position of near destruction from God.  He was correct in saying to Abraham, "thou hast done deeds unto me that ought not to be done." 

Abraham's response to Abimelech when questioned why he did what he did was "because I thought, Surely the fear of God is not in this place, and they will slay me for my wife's sake."  Even for someone as faithful as Abraham and Sarah, yet there were times that their faith waned and they attempted to take things into their own hands.  Rather than trusting that God would watch over them, in this occasion and in the similar episode in Egypt, they had trusted in their own ingenuity.  However, when we trust in ourselves rather than God, we generally cause ourselves problems and make a mess of things.  Ultimately their deliverances came from God and not from their own plans. 

In the above, Abraham reveals to us that Sarah is his half sister.  That explains why what he said and what she said was not directly a lie.  Yet it was deceitful for them to say this and mislead people into believing they were siblings and not spouses. 

Gen. 20:14-16 Abimelech gives gifts unto Abraham and Reproves Sarah

Gen. 20:14 "And Abimelech took sheep, and oxen, and menservants, and womenservants, and gave them unto Abraham, and restored him Sarah his wife. 15 And Abimelech said, Behold, my land is before thee: dwell where it pleaseth thee. 16 And unto Sarah he said, Behold, I have given thy brother a thousand pieces of silver: behold, he is to thee a covering of the eyes, unto all that are with thee, and with all other: thus she was reproved."

To the above passage we make the following observations:

    1.  Abimelech obeyed God when he restored Sarah back to Abraham.  Because Abimelech feared God he did not linger in restoring Sarah.

    2.  Abimelech believed God when God told him that Abraham was a prophet.  Abimelech recognized the superiority of office of the prophet over his office of King.  We do not know how Abimelech gained his office, but we do know that God appointed Abraham to the office of prophet.  Thus, Abraham's office is superior to Abimelech's office.

    3.  In honor of God's blessings upon Abraham, Abimelech gave gifts unto Abraham: sheep, and oxen, and menservants, and womenservants and a thousand pieces of silver.  Abimelech was a wealthy man, but he was willing to give of his wealth to assist the prophet of God on his journey of life.

    4.  Abimelech reproved Sarah.  He did this by gently referring to Abraham as her brother.  Moreover, she was reproved in that Abimelech was gracious and giving unto Abraham and her while she and Abraham had been deceitful.  The scriptures tell us to overcome evil with good: Luke 6:35 "But love ye your enemies, and do good, and lend, hoping for nothing again; and your reward shall be great, and ye shall be the children of the Highest: for he is kind unto the unthankful and to the evil." 

Gen. 20:17, 18 Abraham prays for Abimelech and his household 

Gen. 20:17 "So Abraham prayed unto God: and God healed Abimelech, and his wife, and his maidservants; and they bare children. 18 For the LORD had fast closed up all the wombs of the house of Abimelech, because of Sarah Abraham's wife."

Previously Abraham had interceded on behalf of Lot and God honored Abraham by delivering Lot from the destruction of Sodom and Gomorrah.  Now Abraham prays unto God for Abimelech and his household.  Lot was very close kin to Abraham, but Abimelech was a stranger.  Yet Abraham prayed for Abimelech as well as Lot. 

God answered the prayer of Abraham on behalf of Abimelech and his household and gave to them children which had been withholden from them because of Sarah.