In this week's parsha Avimelech takes Sarah as a wife (20;2).

However, why wasn't Avimelech killed for taking Sarah? The Rambam (Hilchos 

Melachim, 9;14) states that Shechem was killed just for taking Dinah (34;26)! 

Therefore, even though Avimelech didn't even touch Sarah he should have still 

been killed just for taking her like Shechem was for taking Dinah!?!

Rabbi Yochanan Zweig explains that the difference in the 2 cases is that in 

Shechem Dinah was a complete tourist, as the torah (34;1) states that she "went 

out to look over the daughters of the land."  By Avimelech, however, Sarah had 

actually moved to Gerar-as the pasuk (20;1) states: "and he lived in Gerar." And 

why does this make a difference? Rabbi Zweig explains that according to the 

Rambam a king is only allowed to take someone in his country as a wife if she is 

actually living there. Dinah however was only looking around touring the 

land-therefore, Shechem was killed for taking her as wife. Avimelech on the 

other hand was somewhat justified in taking Sarah as she had moved in to his 

country to which he had complete control over. Thus, Rabbi Zweig explains that 

Shechem was killed for merely taking Dinah whereas Avimelech was kept alive 

despite taking Sarah.