Nedarim 8a: Rav Gidel said in the name of Rav: One who says, ‘I will get up early tomorrow and learn this perek, or this masechta’ has vowed a great vow to the G-d of Israel.”
נדרים ח ע”א: ואמר רב גידל אמר רב: האומר אשכים ואשנה פרק זה, אשנה מסכתא זו ־ נדר גדול נדר לאלהי ישראל.
Rabbi Meir Shapiro proposed the Daf Yomi at the first Knessiah Gedolah of Agudath Israel, in Elul 5683 (1923). He had some trouble getting people to accept the idea. Before the opening session of the Knessiah, he presented the idea in a private meeting of the Moetzes. Some were concerned that people would not take it seriously, and would then have less respect for the Gedolei Yisroel after they proposed a revolutionary idea that was not accepted. Therefore they advised that Rabbi Meir Shapiro speak publicly and advance the idea himself.
Another one of the Moetzes members asked, “Suddenly every am haaretz is going to finish Shas and be considered a Shas Yid?” Reb Meir was caught off guard. He had not been expecting an objection like that. Luckily, Rabbi Menachem Ziemba spoke up in his defense and said, “A Yid who finishes Shas is already not called an am haaretz!”
Reb Meir still feared that as he was young and relatively unknown, people would not accept his idea. He met privately with the Chofetz Chaim and asked him to present the idea instead. The Chofetz Chaim replied, “No, you present it yourself. But I ask you to come to the session 20 minutes late.” When Reb Meir walked in, the hall was already packed. The Chofetz Chaim rose in his honor, and everyone else followed suit. After that unusual display of respect, everyone paid close attention to Reb Meir’s speech, and the Daf Yomi proposal was greeted with unexpected enthusiasm. It was decided that the Daf would begin with Berachos on Rosh Hashanah 5684 (1923).
There were many, however, who were afraid to start the Daf Yomi program because of the great responsibility of daily learning. What if they missed a day? Perhaps, they thought, starting the program would be considered a vow, as the Gemara says in Nedarim 8a, “Rav Gidel said in the name of Rav: One who says, ‘I will get up early tomorrow and learn this perek, or this masechta’ has vowed a great vow to the G-d of Israel.” Also, the Gemara says in Sanhedrin 26b, “Thoughts can prevent a person from learning Torah,” which Rashi explains (in his second pshat) to mean that if a person plans ahead too confidently, saying that by such-and-such a date I will finish these masechtas, the plan will likely be unsuccessful. Rather, these people argued, better to simply learn with no stated quota.
These misgivings continued until the first day of Rosh Hashanah arrived, and the Gerrer Rebbe, the Imrei Emes, left his beis medrash after davening, saying, “Now I am going to learn the Daf Yomi!” Following the Rebbe’s example, thousands of Chassidim took upon themselves the Daf Yomi schedule, and thousands more Jews from all over the world followed suit, then and in the 14 cycles since then.
Source: Mayim Chaim – Biography of Rabbi Chaim Kreiswirth, pp. 90-94
[The question of why one who misses the Daf one day is not considered to be transgressing a neder was left unanswered. Perhaps we could suggest an answer based on the rule of בנדרים הלך אחר לשון בני אדם – “When it comes to Nedarim, follow the language of people.” (Nedarim 49a and many other places). The words of a person’s vow legally mean what most people use them to mean. When most people say they are learning Daf Yomi, they mean that once in a while, they might miss a daf and make it up later.
Therefore, if someone makes his own private resolution to get up early and learn a certain daf, that is a neder as the Gemara says. But if someone joins the Daf, they are joining it with the intent of doing what the other Daf learners typically do.
Thus in Elul 1923, everyone was afraid to be the first to accept the Daf, because there would be no precedent to base themselves on, and perhaps it would be a neder to learn every single day. But after Rosh Hashanah 1923, once the Gerrer Rebbe and his close Chassidim accepted it, others could accept it too and their words would mean whatever the Rebbe’s words meant – to learn it on most days.
Alternatively, we could say that the Gerrer Rebbe certainly said “bli neder” when accepting it, so it became the standard that anyone accepting the Daf meant bli neder, although he may not have said so explicitly.
As to the second quote, from the Rashi in Sanhedrin 26b, we could say that Rashi means that one who boasts about exactly how much he will learn is punished either because of his arrogance, or because of ayin hora. But in the case of Daf Yomi, once it was already accepted by many people, one who announces that he is joining is not displaying arrogance, neither does it cause ayin hora.]
Read and Remember 