Beis Shammai say: A man may not divorce his wife unless he found in her an act of adultery, as it says (Deuteronomy 24:1): Because he found in her an adulterous thing. Beis Hillel say: Even if she burnt his food, as it says: Because he found in her an adulterous thing. R' Akiva says: Even if he found another more beautiful than her, as it says (ibid.): And it comes to pass that she does not find favor in his eyes.