GEN 26:7

7 When the men in Gerar [town] asked who Rebekah was, Isaac said, “She is my sister.” He said that because he was afraid to say, “She is my wife.” He thought, “Rebekah is very beautiful, so they will want her. [If I say that she is my sister, they know they will have to negotiate about a bride price because I am her older brother; but if I say that she is my wife, no negotiation will be possible]. They will just kill me to get her.”