According to Rav Zeira in Menachot 40b, the issue with regard to tzitzis for a linen garment is K'sut Leila. Is Rav Zeira concerned with a garment that is designated for night wear which is exempt from tzitzis even by day, or is he concerned with any garment, even one designated for daytime use if worn by night. According to the latter explanation of K'sut Leila, it becomes clear that tzitzis is a time-bound mitzva & women are exempt. Nighttime is excluded from the fulfillment of this mitzva. In this shiur we will explore the three main opinions of the Rishonim on the understanding of Rav Zeira.