Shevuot (Oaths) 28 - Repeated Oaths and Quizzes
If one swore, "I take an oath not to eat this loaf of bread," then again, "I will not eat it," "I will not eat it," and ate, he is liable only for transgressing the first oath. Additional ones do not take effect, since the first one already prohibited the loaf to him. If, however, the first oath is annulled, the second one takes effect.
Aifa studied oaths in the academy of Rabbah. His brother Avimi met him and asked a question, "If one takes an oath that he has not eaten today, and then repeats it, what is the law?" Aifa said, "He transgressed once." "Wrong!" - said Avimi - "These are two false oaths."
Avimi asked another question, "An oath that I will not eat nine figs, an oath that I will not eat ten!" Aifa answered, "Liable for each oath." "Wrong!" - said Avimi - "If he cannot eat nine figs, then he cannot eat ten."
Avimi asked a third question, "'An oath that I will not eat ten figs, an oath that I will not eat nine,' - and then he ate ten, what is the law?" Aifa answered, "He transgressed once, since the second oath is included in the first." "Wrong!" - said Avimi - "The first oath prohibits ten figs, but allows nine, so the second oath is stricter than the first!" - and if he eats ten figs, he transgresses two oaths.
Art: Edmond Lebel - Sellers of figs and nuts