Moed Katan 9A

מותרין לישא ערב הרגל, קשיא לכולהו.

are permitted to marry on the eve of the pilgrimage Festival. This poses a difficulty to all of the opinions, as a wedding celebration ordinarily extends for 7 days, and the majority of the celebration will coincide with the Festival.

לא קשיא למאן דאמר משום שמחה ⁠— עיקר שמחה חד יומא הוא.

The Talmud answers: This is not difficult, as this baraita can be reconciled with all of the opinions. According to the one who said that one may not get married on the intermediate days of a Festival because of joy, i.e., because one must not mix one joy with another, or because one may not put aside the rejoicing of the Festival and occupy himself with rejoicing with his wife, this is not difficult, as the primary joy of a wedding is only one day, and after that, the joy of the wedding will not affect the joy of the Festival.

למאן דאמר משום טירחא ⁠— עיקר טירחא חד יומא הוא. למאן דאמר משום ביטול פריה ורביה, לחד יומא לא משהי איניש נפשיה.

And according to the one who said that one may not marry on the intermediate days of a Festival due to the excessive exertion that the wedding preparations demand, it is not difficult, as the primary exertion is only one day. After the wedding, excessive exertion is not required. And according to the one who said that the reason is due to the neglect of the mitzva to be fruitful and multiply, there is no room for concern: Since there is only one day, the eve of the Festival, when he can get married and save money on the feast, a man will not delay his wedding in order to get married then, lest some unforeseen circumstance arise that will prevent him from getting married on that day. Therefore, according to all the reasons offered, there is no need to prohibit weddings on the eve of a Festival.