A besulah marries on the fourth day of the week.
The Devarim Nechmadim interprets this statement homiletically. The Yerushalmi (Brachos 2:4) states that on the day the Bais HaMikdash was destroyed, the Redeemer was born. The Mishnah alludes to this idea by stating that the Besulas Yisroel, i.e. the Bais HaMikdash, fell on the fourth day, i.e. at the end of the fourth millennia, as a thousand years in HaShem’s eyes is akin to a day. Nonetheless, she remarried immediately, as subsequent to the destruction, the Redeemer was born.