Musar sur Rois 2 2:11

Midrash Shemuel on Avot quotes the opinion of Rabbi Shimon ben Tzadok to the effect that the Rabbi Shimon who told us about the advantages of silence in the above quoted Mishnah was one of the Ten Martyrs. All these martyrs sanctified not only their souls but also their bodies. There are two methods of sanctifying the body. 1) The way of Rabbi Akiva and his colleagues who died on קדוש השם, a martyr's death.This kind of holiness is referred to in the Torah as: והייתם קדושים (11,45). The second method of achieving holiness of the body is referred to in the Torah as: אני ה' מקדשם (21,23). Nadav and Avihu acquired holiness of the body via the second method, i.e. their souls were burned whereas their bodies remained intact. Their departure from this world was similar to that of Chanoch (Genesis 5,24), and Elijah (Kings II 2,11). This is why I believe that the reason their bodies remained intact was that their death was due to the intimacy they had established with G–d. When Rabbi Shimon said that he had not found anything better for the body than silence, he alluded to the instruction given to Rabbi Akiva and the other Martyrs to be silent and accept G–d's decree without question. Only after having made this point does Rabbi Shimon explain in detail what this silence is all about. The Talmud (Berachot 61b) reports that when he was about to die, Rabbi Akiva told his students that he had wanted to fulfill the instruction (Deut. 6,5) to "love your G–d with all your heart, all your soul and all your might," as we recite three times daily. He had wondered when he would finally be able to fulfill the part of "loving G–d with all your soul." By dying a martyr's death he was satisfied that he had finally been granted the opportunity to also fulfill that dimension of loving G–d. It was in this connection that Rabbi Shimon – who was also to become a martyr – said: "study is not of the essence whereas practice is." He referred to the difference between displaying one's love for G–d in theory and displaying it in practice. He also wanted to teach that when the practical opportunity to die a martyr's death does not arise (as in 99% of all lives), G–d will consider the intention to do so, i.e. the fact that one has mentally and emotionally prepared oneself to love G–d to the point where one is ready to die for His Name, as if one had actually done so. This is the deeper meaning of: אני ה' מקדשם "I, the Lord, sanctify them."