And with this, we can explain the statement of the sages (Sanhedrin 91b): "It was taught, Rabbi Meir said, from where do we know about the resurrection of the dead from the Torah? As it is stated, 'Then Moses and the children of Israel will sing this song to Hashem' – it does not say 'sang,' but 'will sing' – from here is a proof for the resurrection of the dead from the Torah." And we have already explained that the children of Israel were saddened by the death of their relatives who remained in Egypt, so Hashem strengthened their spirit by indicating that the resurrection of the dead is still expected, and they could sing with joy [as is accepted in the name of the holy Rabbi Aharon of Belz]. Indeed, according to our words, we can add that from a physical standpoint, they were not worthy of singing such a song, as they had just come out of years of hard labor, with mortar and bricks, work that degrades a person and causes him to be simple. However, their song burst forth and emerged from a very high place, which is the essence of the pure soul, which is not under the influence of the body. The proof of this is the statement of the sages (Sotah 30b), that even infants and fetuses sang this song, which pertains only to the song of the soul, which does not require the conditions of the body and sings by itself.

Thus, the entire community of Israel, men, women, slaves, maidservants, infants, and fetuses, erupted in a song that came from feelings of love and devotion, 'together they all gave thanks and accepted the sovereignty and said, Hashem will reign forever and ever,' as it is written (Psalms 150:6), "Let every soul praise Hashem, Hallelujah."

And this was a conclusive and compelling proof of the resurrection of the dead, for here the souls sang without any assistance from the body, implying that they have life of their own, exist forever, and are destined to live again in the body at the time of the resurrection of the dead.