Our Gemara on Amud Beis continues to discuss the prohibition of improper intentions that can invalidate the sacrifice when thought during the essential services of the sacrifice, such as the slaughtering or sprinkling of the blood. The two basic categories of invalidating intentions are to eat or offer the sacrifice beyond its allowed time, such as from the shelamim sacrifice on day three, or out of its location, such as on non-consecrated grounds outside the walls of the Temple or Jerusalem, depending on the sacrifice.

There is an irony in that the thought about the action invalidates the sacrifice, while the action itself of eating outside of the time or location, though forbidden, does not invalidate the sacrifice. In other words, had someone actually eaten a portion of the sacrifice outside of its prescribed location, while forbidden, the rest of the sacrifice would still be valid. Yet, the intention to do so, during the critical services such as sprinkling the blood invalidates the entire sacrifice. 

How do we explain such a phenomenon? Yeyn Levanon (Avos 3:11) explains that most sins are not done not out of heresy or spite, rather due to weakness in self control. The desire overtakes the person. However, some sins have no benefit and therefore the severity is worse. To actually eat from the sacrifice outside of its time and location is surely a serious sin, but ultimately he was hungry and caved into his desires. Yet the thought of eating or offering the sacrifice at the improper time or location is a desecration with no material benefit, and considered much more severe if not heretical.

In a similar way the idea might be reflected in Gemara Yoma (29a): “Thoughts of transgression are worse than the transgression itself.” A person whose soul is immersed in sinful thoughts is in a much worse spiritual state than one who falls into sin but regrets it and works toward repentance.