Why does it say "Yomam Yetzaveh Hashem Chasdo"?
Rashi: Light will come, and Hashem will command His Chesed for us.
Radak #1: Some say that this refers to ascending for the Regel. On the day, when they were going on the road, Hashem commanded His Chesed. They went safely, and found all their needs on the way.
Radak #2: This is the answer to the Nefesh, which despaired. Do not despair. Hashem will send his Chesed in our days - i.e. days of salvation, which are compared to daylight.
Malbim: Every affliction that came against Yisrael, until it darkened for them and it was night, was a sign for them that at this moment Hashem's light will be revealed, and it will be day; Hashem will command His Chesed.
Why does it say "uva'Laylah Shiro Imi"?
Rashi, based on Mesorah ha'Gedolah: At the time of the affliction, He camps amidst us. Shiro is an expression of encampment; the Targum of "va'Yichan" (Bereishis 26:17) is v'Shara. This is like "va'Yhi Shiro Chamishah va'Alef" (Melachim I, 5:12).
Rashi, from Shocher Tov 5: Yisrael say to Hashem, we remember what You did for us in Egypt. You commanded us one Mitzvah during the day, on Erev Pesach 1 , and we guarded it. At night You redeemed us, and we sang Hallel in front of You. Now we guard many Mitzvos, and You do not redeem us! This is why it says "l'Kel Sal'i Lamah Shechachtani" (verse 10).
Radak #1: When they were ascending for the Regel, at night they lodged and sang and praised Hashem.
Radak #2: [He tells the Nefesh] now that it is night (Galus), let us sing to Hashem for all the Chesed that He did with our fathers, and that He does with us every day in exile.
Malbim: The night before the miracle, which is it is still night, I already sang for the Chesed that He will do, and I prayed for it.
Why does it say only one Mitzvah? We were command to take Kelim from the Egyptians, to take an animal for Korban Pesach, to guard it, slaughter it, put the blood on the doorposts, and to eat it roasted with Matzah and Maror, while ready to leave, not to leave over meat, and to burn the leftover (Shemos 11:2, 12:3-11)! Perhaps taking Kelim does not count, for it was for our physical benefit; the rest are all details of the Mitzvah of Korban Pesach. (PF)
Why does it say "Tefilah l'Kel Chayay"?
Radak: [He tells the Nefesh] let is pray to Kel of our life, that He keep us alive until the redeemer will come, and we will see His salvation.
