Rav Naḥman bar Isaac noted that both and begin, "And the Lord spoke to Moses in the wilderness of Sinai," and deduced that just as happened (in the words of that verse) "on the first day of the second month," so too happened at the beginning of the month. And as addressed the Passover offering, which the Israelites were to bring on the 14th of the month, the Gemara concluded that one should expound the laws of a holiday two weeks before the holiday.