Genesis 20

There are several different concepts of our faith that is illustrated in this passage.

The first is all of us being a part of God's family. God calls us His sons and daughters, and so we would call one another brothers and sisters in Christ. The first account of this title as people being brothers and sisters is found in this chapter when Abraham explains to Abimelech that Sarah, his wife, is still considered his sister too as they are adopted into God's family with God as our Heavenly Father.

Genesis 20:12
Besides, she really is my sister, the daughter of my father though not of my mother; and she became my wife.

Another concept is of God's justice to those who sin. We have been saved by the power of Christ, and so even when we sin, we can repent and learn from our mistakes and God will not punish us. When we clearly have made an innocent mistake or have done something by accident, we can be assured that God knows and would not pass on the consequences to us. This is illustrated when Abimelech speaks to God in his dream regarding his capture of Sarah, believing she wasn't married at first. God is fair. Knowing that Abimelech only took her thinking she was Abraham's sister but not his wife, God gave Abimelech the chance to right his actions by returning Sarah to Abraham. He did that and was blessed. This is the same for us: if we do something wrong (mistake or intentional), God always gives us a chance to do the right thing to correct what you did and through that God continues to help you grow into a maturing disciple.