Therefore, explains the Kohelet Yitzchak, when a person performs a Mitzvah, he faces two trials. The first is before the act, when the Satan stands against him and places obstacles before him, doing everything to prevent him from performing it. The second is after the act is performed. Even if he overcomes his yetzer hara and performs the Mitzvah, he is still not safe, because then the Satan will strive with all his might to uproot that Mitzvah. This is even a greater business for the Satan than at the onset, as it is clearly a greater transgression to regret the Mitzvah performed than not to perform it at all. Therefore, the danger is greater after the act than before it.
Tying this back to Avraham and Sarah, Kohelet Yitzchak says this was the plan of the Satan. Initially, when Avraham Avinu went to Har HaMoriah, the Satan shook the world, as stated in the Midrashim. The Satan knew the great value of the Akeida, and that the success of the chosen nation depended on it, and accordingly, he increased the obstacles and pitfalls along the way. When he saw that he achieved nothing, and that Avraham did not listen or pay attention to him at all, he then gathered his remaining strength and sought to uproot the Akeida altogether. What did he do? He went to Sarah and frightened her with his lies, and she died. He did this so that Avraham would regret the act of the Akeida and be considered as regretting his act of Mitzvah. He wanted Avraham to say: "Why did I perform the Akeida?! If I hadn't bound Yitzchak, she wouldn't have died!"
But Avraham knew the Satan well and knew his schemes and tactics. He was not affected by this at all, and his spirit sustained him in his illness, and he came with a joyful heart over the act of the Akeida to eulogize Sarah – meaning, to recount her good deeds. But to weep for her? Only a little. Therefore, the word תָ הּ כּ ֹ וְלִבְ is written with a small kaf, so that people would not say when they saw him wailing and lamenting over Sarah's death that he now regrets the act of the Akeida because through it he lost his uniquely righteous and wife. Therefore, he did not weep greatly, and for this same reason, it is also written לִ סְ פּ ֹד (to eulogize) first, because the main thing for him was the eulogy and to recount her good deeds; not the weeping.
