Quotation על נדה 61:40

יששכר חמור גרם, "Issachar is a bony donkey, etc." We learn in Nidah 31 that the meaning of the verse is that G'd had a hand in the conception of Issachar having guided Jacob's donkey to the tent of Leah on that night (Genesis 30,16). Just as Jacob had not remained in his regular abode that night, so Issachar, the son who had been conceived during that night, would be "crouching between boundaries." Inasmuch as Issachar is the model of a person who devotes his life to Torah study, Jacob alluded to the phenomenon that Yeshivah students have a habit of moving from place to place. Every action which is not proper produces consequences which reflect that impropriety. Leah's action appeared too forward for the conduct associated with the traditional way of life of Jewish women, even though her intention was wholly honourable. In spite of the discomfort associated with the lifestyle of the Yeshivah student, he does not let this diminish the effort he lovingly devotes to Torah study.