As G‑d instructed them, Moses and Aaron presented themselves before Pharaoh and his court, demanding that he release the Jews from slavery. Pharaoh requested proof that they were indeed sent by G‑d. As G‑d had instructed him to, Moses told Aaron to cast his staff to the ground, transforming it into a serpent. But Pharaoh was unimpressed by this marvel since his sorcerers were also able to do it. So G‑d told Moses to transform the Nile River’s water into blood, as the first of the ten plagues.
Warmth and Enthusiasm
הִנֵּה אָנֹכִי מַכֶּה בַּמַּטֶּה אֲשֶׁר בְּיָדִי עַל הַמַּיִם אֲשֶׁר בַּיְאֹר וְנֶהֶפְכוּ לְדָם: (שמות ז:יז)
[G‑d instructed Moses to tell Pharaoh,] “I am now going to strike the water in the river with the staff in my hand, and it will turn into blood.” Exodus 7:17

The first of the ten plagues was the transformation of cold river water into warm blood, signifying the transformation of cold indifference toward Divinity into warm enthusiasm for it. This had to be the first of the plagues, because indifference would have prevented the Egyptians from being affected by any further demonstrations of G‑d’s power and involvement in life.

A similar lesson applies to anyone striving to leave the slavery of their inner “Egypt” – the tyranny of their material drives and not-yet-refined bodily desires. Our first step in this process is to replace any cold indifference to all things Jewish and holy with warm, passionate enthusiasm for G‑d, His Torah, and His commandments.1