Ketubot 60 - Nursing a child
Abaye's sharecropper wanted to make engagement with a woman whose husband recently died, and who was still nursing a child for the previous fifteen months. He came to Abaye to ask whether this is allowed. Abaye gave him many reasons why it was permitted.
Firstly, Rabbi Meir requires to wait for twenty four months of nursing, but Rabbi Yehudah only needs fifteen months, and the law is always like Rabbi Yehudah against Rabbi Meir. Secondly, many other Sages also allow this. There were other reasons as well.
However, Rav Yosef, Abaye's teacher, corrected him: Abaye forgot another rule - when Rabbi Meir suggests a protective decree, the law always follows him. Abaye ran after his sharecropper for three miles, and some say - for one mile in the sand, but could not overtake him.
Abaye then said: "This mistake happened to me, because I should not have decided the law, even if it seemed obvious to me, in the vicinity of my teacher, for this is disrespectful."
And what is the reason of those who prohibit such marriage? - If the woman then becomes pregnant, the milk may become unfit for nursing, thus endangering the baby.
Art: Woman Nursing an Infant by Pieter De Hooch