"If you walk in my statutes and guard my commandments and perform them, I will give rain in its season the earth will give forth its produce and the tree will yield its fruit..."
"If you walk in my statutes," What is the "walking in the statutes?" I would think this is referring to fulfilling the mitzvos; when the verse goes on to say: "and guard my commandments" this is clearly referring to fulfilling the mitzvos! If so, what did it mean when it mentioned "walking in the statutes?" Struggle diligently in Torah study...
"and guard my commandments," -- Struggle diligently in Torah study in order to guard and perform.
To Rashi, the meaning of the verses becomes: "If you will struggle diligently in Torah study in order to guard and perform the commandments, I will give rain in its season the earth will give forth its produce and the tree will yield its fruit..."
The reward is difficult to understand... for keeping the commandments there will be tangible reward in this material world? Didn't the Talmud say: "The reward for mitzvos is not in this world?" (Kidushin 39b)
Similarly, the Talmud states (Moed Koton 28a): "Children, Length of days and wealth are not dependent on merit [alone] but on 'mazal' (fortune)."
However, the Tosafos commentary there mentions that "a great mitzva is different," and can change one's "mazal." The legal commentary Elya Rabba explains that this is Rashi's meaning here, as well. Amailos Batorah -- diligent application to Torah studies -- is a "great mitzva" that can help inspire a change in one's 'mazal.
Indeed, Torah study is unlike any other study. In Medrash Tanchuma to Parshas Noach, the Rabbis describe to what lengths the Torah Scholars must go: "The people who walked in darkness -- saw a great light," refers to them, because they deny themselves sleep, struggling over obscure passages in the Talmud -- until the great light of understanding comes. They deny themselves food and drink and pleasures in this world, instead spending their time toiling, struggling to understand the Torah.
"The soul of the working man works for him, for his mouth forces him." The soul of the man striving for Torah works for him, for while he works in one area of Torah study, his soul strives for him in another area. (Sanhedrin 99b).
The Elya Rabba explains: One who constantly reviews his learning -- it will become orderly for him. This is the meaning of the prayer (in the daily blessings over Torah study): "Please, G-d, make the words of Your Torah sweet in our mouths... so that we... may all know Your name and learn Torah for Your name's sake..."
"So that we may all know Your name:" All the Torah is the Name of G-d. Another explanation: The Zohar states (like Rashi and Tosaphos quoted above), that diligent study of Torah can change a heavenly decree. Therefore, we will know G-d's name, and not the name of the "mazal" (literally, a constellation).
(c) Rabbi Yaakov Bernstein and Genesis, '97