Why did Hashem instruct Aharon to strike the water for the first two Makos?
Rashi and Targum Yonasan: Because the water protected Moshe when his mother placed his basket in the river (See Shemos 2:4). Consequently, for him to strike it would have demonstrated a lack of gratitude. 1
Moshav Zekenim (to 8:2): Aharon was Moshe's Shali'ach, so he performed the Makos that struck the land. Moshe himself performed the Makos that came from the sky.
Gur Aryeh: (Why does that make a difference? The water is but an inanimate part of Creation!) Rather, the Torah is teaching us proper conduct -- "Do not throw a clod of earth into the well that you have drank from" (Bava Kama 92b).
What is the difference between "Naharosam", Ye'oreihem" and "Agmeihem"?
Rashi, Targum Onkelos and Targum Yonasan: "Naharosam" means 'their rivers', "Ye'oreihem", and "Agmeihem", 'their man-made canals' (which flowed and watered their fields) and "Agmeihem", 'their pools (or reservoirs)' (gatherings of water th do not flow).
"Ve'hayah Dam be'Chol Eretz Mitzram". What is tis coming to include?
Rashi: It includes water in sinks and in bath-tubs.
What are the connotations of "u'va'Eitzim u'va'Avanim"?
Rashi and Targum Yonasan: It means the water that had been poured into wooden and stone vessels, would turn to blood as well.
Oznayim la'Torah (citing Midrash ha'Gadol): It means the blood would actually ooze out of wood and stone. 1
Oznayim la'Torah: This was measure-for-measure, because the Egyptians forced the Jewish slaves to place babies in the walls when they were short of bricks.
