One of the unfamiliar ideas of the Gra is that every word of learning Torah equals all the other commandments. The Mishna in tractate Peah brings this in short without going into it but the Gemara Yerushalmi explains in great detail that every word of Torah equals all the other commandments. That means that even if one would keep all the commandments of the Torah with the greatest love and fear of God, with the greatest degree of burning love and attachment with God, still if you would place all that one one side of a scale and just one word of Torah on the other, they would be equal in weight. All the more so if you would place two words of Torah on the opposite side that scale would immediately tip over to the side of the two words of Torah. however if there is a commandment that can not be done by someone else, then one ought to interrupt learning to fulfill it and then return to learning as brought also in the Yerushalmi where one person sent his son to learn Torah in Tiberias and heard that he was involved in helping burying the dead. He asked his son' "Did I send you there to bury the dead or to learn Torah? [The Yerushalmi says when the commandment can not be done by another, one should interrupt one' learning. however there is also a principle one involved in a mitzvah doe not have to interrupt to do another. This is the case with the penny of Rav Josef. That is since one is guarding a lost object, he doe not have to give a penny to a pauper. ]
What counts as Torah? See the letter to Yemen of the Rambam: "Just as there is no adding nor subtracting from the Written Law, so there is no adding nor subtracting from the Oral Law."
That means that just as one can not add to the books of the prophets from Moses until the last prophets of the First Temple period, so one can not add the the Oral Law as redacted by the Tenaim of the Mishna and Amoraim of the two Talmuds. The Gemara also mentions this: "Ravina and Rav Ashi are the end of rendering a halachic decision." רבינא ורב אשי סוף הוראה
I would like to add here that there are two ways of learning Torah. One is that of Reb Chaim of Brisk which is global or you might say a hawk eyes approach that learns the whole Shas [Talmud] by learning one page. The other is that of Rav Naftali Yeager of Shar Yashuv and David Bronson which is an electron microscope approach. You can least see the Reb Chaim approach in his writings and the other great sages of the Litvak world. The other I think is not so available. I myself could get to this approximately by learning one Tosphot for about a month and then I could start to see the infinite depth of Tosphot. .
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