The parsha of פרה אדומה begins with the words “זאת חקת התורה”, and the universal question is asked: Why does it state “חקת התורה” and not “חקת הפרה”? After all, we are specifically discussing the laws of the Parah Adumah, and it would be more appropriate to introduce the parsha as pertaining to the halachos of the Parah?

     R' Meir Premishlaner zt”l explains that before a person performs a mitzvah, his yetzer hara comes to him and attempts to dissuade him with excuses such as, "Are you really worthy of doing this mitzvah? Do you think you can properly do it? Why bother?" If this fails and the person goes ahead with the mitzvah, the yetzer hara comes afterward and tells him, "Look how great you are. How worthy and special you are!" - thereby instilling the middah of arrogance, within him. One must be careful, before and after a mitzvah, from the Satan.

     This is the meaning of Rashi's words, "A decree from before Me and you do not have a right to stray after it" - One must be firm in his commitment to ward off the evil designs of the Satan before he does a mitzvah, and even after he has completed the mitzvah, do not let the yetzer hara get to you. In this vein, we understand the lesson that applies to all areas of the Torah and mitzvos, not just to the פרה אדומה. Thus, the posuk writes “זאת חקת התורה” - "Laws of the Torah."