הֲלֹ֨א ה֤וּא אָֽמַר־לִי֙ אֲחֹ֣תִי הִ֔וא וְהִֽיא־גַם־הִ֥וא אָֽמְרָ֖ה אָחִ֣י ה֑וּא בְּתָם־לְבָבִ֛י וּבְנִקְיֹ֥ן כַּפַּ֖י עָשִׂ֥יתִי זֹֽאת׃
그가 나더러 이는 내 누이라고 하지 아니하였나이까 그 여인도 그는 내 오라비라 하였사오니 나는 온전한 마음과 깨끗한 손으로 이렇게 하였나이다
Rashi
גם הוא ALSO SHE HERSELF — The word “also” presupposes that others also said the same: it serves to include her servants, cameldrivers and assdrivers — all these I asked and they told me, “He is her brother” (Genesis Rabbah 52:6).
Or HaChaim
בתם לבבי ובנקיון כפי "I acted with innocence and integrity." Avimelech said these words in the event Sarah was married, but not to Abraham. He claimed that if that were so what would Abraham have gained by declaring that she was his sister? This exonerated him from the death penalty, i.e. בתם לבבי. When he added בנקיון כפי, he pleaded that he was not guilty of the death penalty for robbery either, though we have a ruling both in Sanhedrin 57 and in Maimonides (the chapter quoted above) that a Gentile who commits robbery is guilty of the death penalty. It does not matter that the robbery is an act of kidnapping as distinct from stealing. The Talmud deduces this when it discusses the status of a prisoner of war who is considered as the victim of robbery or stealing. Accordingly, from the moment Avimelech took Sarah against her will he became guilty of the death penalty. Avimelech claimed that he thought both Abraham and Sarah were pleased at his taking Sarah for a wife. After all, he was the king and it meant social climbing for them both.