Commentaire sur La Genèse 12:13

למען ייטב לי בעבורך THAT IT MAY BE WELL WITH ME FOR THY SAKE — they may give me presents.

למען ייטב לי, so that when you will say that you are my sister, each one will entertain the hope that I will agree to your marrying them. Therefore, none of them will have any reason to kill me. Rather, he will seek my approval by offering me a dowry for you. It was the custom in those days that the father of the bride would be bribed with money or its equivalent to agree to let his daughter marry someone. This also explains why the Torah speaks of מהר ימהרנה in Exodus 22,15-16, i.e. “he (the seducer) shall pay a heavy dowry,” and why the option to refuse such a marriage is not so much the girl’s but her father’s, as we see from the verse following.

למען ייטב לי בעבורך. In order that I will receive benefit on your account. Abraham explained why he asked Sarah to describe him as her brother and not as some more distant relative or a total stranger. If Abraham's status were anything less than Sarah's brother the Egyptians would not have any interest in securing his goodwill. Abraham may have had yet another motivation for insisting that Sarah describe their relationship to each other instead of he himself. His own words would not convince the Egyptians as they might construe them as a stratagem to be wooed with gifts. The plain reason is no doubt that he was afraid that if he were to say he was her brother and she would say nothing, sooner or later Sarah might make a comment which would reveal that there was a husband-wife relationship between her and Abraham. When Abraham added that וחיתה נפשי, that his soul would remain alive due to the stratagem of Sarah describing him as her brother, he did not have in mind his mere physical survival. If that had been his intention he would have said ואחיה, "so that I will survive." The word וחיתה נפשי is an allusion to Sarah's remaining spiritually uncontaminated. We have a tradition (Proverbs 13,25) that צדיק אוכל לשובע נפשו, that the reason a righteous person consumes physical food is not to indulge his senses but to satisfy the needs of his soul to carry on his task in life. Abraham was motivated by similar considerations.