fom: http://www.thebricktestament.com
There was a famine in the country -- different from the previous famine which took place in the time of Abraham -- and Isaac went to Abimelech, the Philistine king at Gerar.
When the people of the place asked him about his wife, he replied, She is my sister, because he was afraid to say, She is my wife, thinking, The people of the place will kill me because of Rebekah, because she is beautiful.