Genesis, Chapter 26, Verse 7
When the men of the place asked questions about his wife, he answered, “She is my sister.” He was afraid that, if he called her his wife, the men of the place would kill him on account of Rebekah, since she was beautiful.
So Isaac (whom was bound as a sacrificial offering to God) the only son of Abraham, now is grown, has a wife and is pulling the same trick with the men who desire his wife-stating she is my sister.According to the Jewish Encyclopedia, the recurring story has a unified purpose:
"From the point of view of the history of culture these episodes are very instructive. But it is not very probable that Abraham would have run the risk twice. Moreover, a similar incident is reported in regard to Isaac and Rebecca. This recurrence indicates that none of the accounts is to be accepted as historical; all three are variations of a theme common to the popular oral histories of the Patriarchs. That women were married in the way here supposed is not to be doubted. The purpose of the story is to extol the heroines as most beautiful and show that the Patriarchs were under the special protection of the Deity."
Another lesson we can take from this is that Isaac here was dealing with men that had no fear of God. Men who take what they want and will kill to get it. Isaac here could not fight them because he was not strong enough. Isaac could not leave because there was a famine. So he sought to deceive. Yet, even in his weakness God was with him and when Abimelech, the righteous king, discovered the truth put him under his royal protection; thus saving him from danger. Righteous men & nations always seek to protect the weak.