This day, the Lord, your God, is commanding you to fulfill these statutes and ordinances, and you will observe and fulfill them with all your heart and with all your soul. (26:16)
Rashi explains: Every day, you shall regard the commandments as if they are brand new, as though you are just today being commanded regarding them! [Tanchuma 1]
We also have another Posuk in this Parsha: “And you do not turn away from any of the words... right or left, to follow gods of others to worship them.” (28:14) The Torah is relating a powerful message: If one turns aside even slightly from the words of Hashem, this is considered actual idol worship. The Seforno on the Chumash interprets “to follow other gods” as being a reference to one who performs mitzvos out of habit, or in response to peer pressure. Someone overly pleased with themselves and their situation in mitzvah observance is equivalent to rebellion against Hashem. One must serve Hashem with conviction and full commitment at all times, not only when it is convenient to do so.
Dovid Hamelech says: Do not cast me away at the time of old age. However, the Rebbe of Druhabitch in his Sefer Eizor Eliyahu offers a Chassidish insight. The nature of a person is to always do with fervor a new project, or new commandment. We see the bar Mitzvah boy feels elevated and commits to perform the mitzvohs with enthusiasm and dedication. Yet as time passes everything fizzles, as it becomes an old act. This is what Dovid is asking Hashem: I should not perform your commandments as they are old ones. I beg that they should always be seen as new mitzvohs, and I should do them with fervor.
There is a famous Vort from Hagaon Rav David Povarsky z’’l of Ponivizh on this subject. In Parshas Toldos we see that Yitzchak and Rivka both stood in prayer to Hashem, beseeching Him to grant them a child. Hashem listened to Yitzchak's prayer because there is no comparison between the prayer rendered by a tzaddik ben tzaddik, the righteous child of a righteous person, and that of a tzaddik ben rasha, righteous child of a wicked person. Why? One would think that Rivka, as the righteous child of a wicked parent, Besuel, had attained a greater achievement than Yitzchak, whose roots were deserving reward.
Rav Povarsky, cites a pasuk in Yeshayah 29:13 as basis for his explanation. The Navi says: "And the Lord said: 'Because this people has come near; with their mouth and with their lips they honor Me, but their heart they draw far away from Me, and their fear of Me has become a command of people, which has been taught.'" This gives the impression that the critique of the people was their complacency in serving Hashem. In other words, they put on Tefillin and observed Shabbos and all of the other mitzvohs. The problem was that they did not display any enthusiasm. They acted by repetition; the manner that they put on Tefillin yesterday was the same way in which they put it on today - without excitement or fervor.
Rav Povarsky explains that when one emulates the observance of his predecessor or parent, without adding any creativity of his own, he is guilty of complacency. A Jew must grow spiritually. To do this, he cannot retain the status quo of observance. The people basically continued observing as they and their predecessors had in the past. They remained carbon copies of those before them without initiating anything of their own. When Mitzvohs are done with all your heart and with all your soul, in these Mitzvohs will elevate the person to higher levels in spirituality.
In order to come closer to Hashem, one has to have fire in his actions, just as the altar always had a fire burning on it. The fire in you when doing mitzvhos will burn the strength of the Yetzer Hara.
(Yehuda Z. Klitnick)
