
Shaarei Tefila
The Gemara says that today, the gates of tefila are closed, but the gates of tears and ona’ah — one who is pained with words — are still open. (Bava Metzia 59a) This raises a number of questions. First, how can we say that shaarei tefila (the gates of prayer) are closed? Of course the gates of tefila are not actually closed; it’s just harder to get through. It’s as if no one hears you at the door. If you don’t knock hard enough, you have to knock harder to be answered. Today, we have to knock harder. (Toras Chaim, ibid.)
However, when someone has been hurt by words, the gates are open for him. The Gemara brings the following example.
Tanur Achnai (Bava Metzia 59a-b)
Rebbi Eliezer and the Chachomim debated the status of an oven made from pieces and cemented together. Rebbi Eliezer held that it retained its purity, but the Rabbis held that it was susceptible to impurity. Rebbi Eliezer would not give in, and used miraculous phenomena to prove that he was correct. Rabban Gamliel and the beis din excommunicated him for not abiding by the majority. Rebbi Eliezer’s wife (who was Rabban Gamliel’s sister) would not let him say tachanun prayer, fearing for the death of her brother (as will be seen). She made a mistake regarding Rosh Chodesh. The Gemara says that it was Rosh Chodesh, but they were ma’aver the chodesh, meaning that there would be two days. She didn’t realize that the real day of Rosh Chodesh would be the second day, but thought that this first day was the real one. So she assumed that he would not say tachanun, (1) and didn’t watch over him. He did say tachanun; she ran in and said, “Stop! You’re killing my brother!” They then heard the announcement that Rabban Gamliel had passed on. “How did you know?” he asked. She answered, “I have a tradition from my father’s household that the gates of ona’ah are not closed.”
The tachanun tefila is indeed very potent. (2) Rebbenu Bachya links it to Moshe Rebbenu falling to his face (whereupon he was quickly answered with the downfall of his enemies). Rebbenu Bachya writes that Rebbi Eliezer learned from Moshe the power of tachanun. (Parshas Korach) Tachanun arouses the severe forces of din — justice (Biur Halevush to Rakanati, Parshas Korach). It’s clear that Rebbi Eliezer had no intent to harm his brother-in-law; nonetheless Rebbi Eliezer had been hurt, and the gates of pain are not closed.
Rosh Chodesh
We see that Rebbi Eliezer said Tachanun on the first day of Rosh Chodesh (according to Rashi; see further the Maharsha, Bava Metzia 59b). Today we have a set calendar (and there is a decree to have two days of Rosh Hashanah); in ancient times it wouldn’t be known which of the two days was actually sanctified. Rebbi Dosa davened on Rosh Hashanah, “Fortify us … either today, or tomorrow.” The second day he would daven “Fortify us … either today, or yesterday.” He did the same for Rosh Chodesh. It’s clear that regarding Rosh Hashana and Rosh Chodesh we were doubtful as to which day of the two was sanctified.
The Chavatzeles Hasharon noted that these statements seem to contradict the story of Rebbi Eliezer. He said the tachanun prayer on the first day of Rosh Chodesh! Clearly, it was not a doubt at all to him… He treated the first day as a normal weekday. The Beis Yehuda (3) writes that Rebbi Eliezer was different. He was familiar with the cycles of the moon and the true calculation. Thus, even though they treated the first day as Rosh Chodesh, he said tachanun because he knew the truth.
Simcha
The Sefer Yire’im (Simon 227) writes that it’s a mitzva from the Torah to rejoice on Rosh Chodesh. Even though it seems contradictory to have simcha on Rosh Chodesh Av (simcha is not allowed during the initial nine days of the month), the Gemara refers to Rosh Chodesh Av as the festive day (Shevuos 10a).
Perhaps the simcha of Rosh Chodesh is because of the korban which is only on the second day. (See B’midbar 10:10 — “On the day of your simcha and set seasons and roshei chodeshim you will sound the trumpets for your korbanos…”) Chavatzeles Hasharon pp. 901-902. This again will help explain Rebbi Eliezer: He knew that the simcha of Rosh Chodesh would be on the day the sacrifice would have been brought.
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1.The tachanun prayer is not said on special occasions, such as Rosh Chodesh.
2.The Asarah Ma’amaros (Chikur Din 1:23) writes that the climax of tefila is the tachanun prayer.
3.Cited in Otzar Meforshei Hatalmud to Bava Metzia, 59b.


