1)
Why does it say "Yomam ha'Shemesh Lo Yakeka"?
1.
Radak: This refers to "Hashem Tzilecha" (5). He shades you, lest heat of the sun harm you.
2)
What Shemirah is needed from the moon at night?
1.
Radak: The moon is cold and moist. Heat and cold cause illnesses. Malbim - even though the harms of the sun and moon are opposite, Hashem guards from both.
