There are some lessons we never learn no matter how old we are. For Abraham, that lesson is not to lie about his wife Sarah.
Reading Genesis 20 is like reading a déjà vu of Genesis 12:10-20. For Abraham told the half-truth to the rulers of the lands he sojourned to that Sarah (Sarai in chapter 12) is his sister in both incidences. While it is true that Sarah is his half-sister, he hid the part that she is also his wife. Apparently, he did this on purpose because she is attractive and he fears that people will kill him for her. (Genesis 12:11-13) He even asked her to lie with him. We don't know why he wanted to make such a lie. Biblical scholar Umberto Cassuto "suggested that Abram (later Abraham) hoped that by claiming to be Sarai's (later Sarah) brother he could fend off suitors by promises of marriage without actually giving her away." (Gordon J. Wenham, WBC: Genesis 1-15) While there are some accounts in Genesis supporting this view, (such as 24:55 and 34:13-17) it doesn't justify the fact that he was risking Sarah instead of protecting her as her husband. Other than this point, I would also like to point out his lack of faith.
It is understandable that moving into a foreign country as a stranger without the supports of relatives is a scary thing. But God has promised him since the very beginning of his journey that He will be with him and bless him in Genesis 12:2-3. God didn't just promise him once; He promised him several times, each time reveals more and more details to him. In Genesis 15, which is the third time that God gave Abraham His promises, He even made a covenant with him. In this incidence, God specifically told him that "a son who is your own flesh and blood will be your heir." (Genesis 15:4, NIV) God makes it even clearer in chapter 17 that "As for Sarai your wife, you are no longer to call her Sarai; her name will be Sarah. I will bless her and will surely give you a son by her. I will bless her so that she will be the mother of nations; kings of peoples will come from her." (17:15-16) The whole purpose of giving him a son is so "all nations on earth will be blessed through him." (18:18) So Abraham knew it all the time that God would give him a son. If Sarah became other people's wife, wouldn't his distrust hinder God's plan? Though we know that no one can stop God's plan from happening, this still doesn't justify the sin he committed and almost got other people committed. In both instances, the two rulers who don't know God proved to be more noble and honest than Abraham. He was publicly humiliated in both cases. If God didn't intervene in both scenarios, His name would be damaged, and that will be the worst situation.
Have you seen that sometimes, unbelievers act more align with the biblical teachings than Christians? What do you think the reason is? Share your experiences and thoughts with your partner. Pray for each other that the Holy Spirit will empower us so that we have the faith to trust in God's promises even when it is frightening.