Eruvin 63: Why Joshua Died Childless

Regarding the prohibition of answering halakhah in the presence of one's teacher: R. Eliezer tells his wife, Imma Shalom, that he doubts the one who taught halakhah in his presence would make it through the year. Which comes to pass. Which is plenty eerie - and he credits his prediction on this tradition that one is not allowed to teach halakhah before his teachers. Plus: The case of Yehoshua ben Nun, who indeed answered in the presence of Moshe... Or alternatively, his punishment ends up being "midah k'neged midah" - in that he prevents people from fulfilling "be fruitful and multiply," and he did not father children. And he's accused of not devoting enough time to learn Torah. Interestingly, the verse that teaches how all-consuming the study of Torah should be is from the Book of Yehoshua.