םימי ז הצמ
There is an obligation from the Torah to eat matzah the first night of Pesach. All the rest of the Pesach days there is no obligation but if one eats matzah he fulfills a mitzvah (Vilna Gaon Chasam Sofer etc). The question arises why didn't the Torah make it an obligation to eat matzah seven days? One is going to wash to make a Motzei anyway so why let it not count as an outright mitzvah obligation? In the Haggadah Shaarei Leil Haseder he answers with a gemarah Berachos 35
ן משום רבי יהודה ברבי אלעאי בא וראה שלא כדורות ðה אמר רבי יוחðואמר רבה בר בר ח יסין פירותיהן דרך טרקסמון כדי לחייבן ðים היו מכðים דורות הראשוðים דורות האחרוðהראשו יסין פירותיהן דרך גגות דרך חצרות דרך קרפיפות כדי לפטרן מן ðים מכðבמעשר דורות האחרו י הביתðאי אין הטבל מתחייב במעשר עד שיראה פðהמעשר דאמר רבי י
One is not obligated to give maaser from his produce until he brings it through the front of his house. However if he brings it in his house through the roof he is רוטפ. The gemarah remarks about comparing the different level of righteousness the previous generations had which the present generations lack. Previous generations brought their produce through their door, in contrast to the present generations they brought it through the roof. The question is that the "present" generations are talking about Taanim. They were in such a low caliber that they sought ways to being free from mitzvos? Secondly it would only free them from a Torah mitzvah but from the Rabbanim even brought in from the roof they still woiuld be required to tithe their produce before eating so what did they gain?
The explanation is as follows. The gemarah in Kiddushin 31 explains that גדול המצווה ועושה ממי שאינו מצווה ועושה that one who is commanded to fulfill a mitzvah is greater than an individual who is not commanded in it. Tosfos explains that the reason is because when one is obligated to fulfill the command of the Torah the yetzer harah will fight him tooth and nail not to do it. This is in contrast to one who is not commanded at all because then the yetzer hara won't bother him that much even if he is still commanded from the Rabbanan.
It was not that these Tanaim were looking for a way to free themselves from the mitzvah because they were still commanded from the Rabbanan to fulfill it. Rather they wanted to free themselves from the harassment and challenges with which the yetzer harah would attack him and they felt they might not be strong enough to overcome it. The same reason applies to the question why didn't the Torah obligate us to eat matzah for seven days? We can't eat chametz anyways and we will wash on matzah anyway why not be generous in fulfilling more obligations from the Torah? The answer is that if it would be a דאורייתא for seven days the yetzer harah might get the best part of us and somehow make us miss the chiyuv of one of the seven days and then we would get an aveirah. Therefore Hashem stopped a chiyuv mitzvah after the first night leaving the rest of the days as voluntary mitzvah that you get reward if you do it and with little hassle and fighting with the yetzer harah ak"d.
With this explanation we can understand what the Torah commands from us when it states to love Hashem בכל לבבך with all your heart. Chazal explain it means even with your yetzer harah. How does one serve Hashem with his yetzer harah? One example is brought above. The previous generations didn't look for the route where the yetzer harah would not start with him. They were ready to be harassed and use all their resoources and strength to demonstrate their love and mesiras nefesh to Hashem. This is called using their yetzer.
There is a story told of Rav Chaim Ozer who was sitting with a friend in the Succah when he excused himself because it was a little cold for him. In five minutes he retuned to sit with his guest. His guest was surprised of his return and said המצטער פטור מן הסוכה you don't have to sit in the Succah if it is too cold. Rav Chaim smiled and said I am pattur from succah because I am מצ רעט but that does not free me from הכנסת אורחים. He used his yetzer harah to show his love to Hashem and Torah like the previous generations.
This could also explain when we say in the אטח לע for the aveirah of רציב הרע. Isn't every aveirah with the yetzer harah so why is it singled out? First we must understand that the word חטא doesn't really mean sin but missing the mark as the Rishonim explain. Therefore according to the above we can explain that this is referring to one who chose not to enter a chiyuv from the Torah for that would make a harder challenge for him
