Aish Da’at: Vaeira III
“For this time I shall send all My plagues against your heart, and upon your servants, and your people, so that you should know that there is none like Me in all the world.” (Exodus 9:14) We learn from this verse that the plague of the Slaying of the First Born was equal to all the other plagues combined. (Rashi)
Many have asked why God would refer to the Slaying of the First Born at this point of the story, when He is describing the plague of Hail.
We can divide the 10 plagues into four sections, some of which were solely at the Hand of God, others that were performed through Moses or Aaron, and some through all three.
The first three plagues, Blood, Frogs, and Lice, were brought about by Aaron. The fourth and fifth plagues, Wild Beasts and Pestilence, were directly imposed by God. The sixth plague, Boils, was performed by God, Moses and Aaron. Hail, Locusts, and Darkness were brought by Moshe’s hand. However, the Slaying of the First Born was imposed directly by God alone.
The Zohar (Volume II 37b) teaches that Pharaoh calculated the ten plagues, their order and how they would be imposed.
Pharaoh expected Hail to be imposed directly by God, and was shocked when he saw that Moshe brought down the Hail. He wanted to understand why the expected pattern was broken.
God therefore says, “For this time,” meaning, this plague, the Slaying of the First Born, will be so devastating that you will no longer fight Me, and I will impose all ten plagues. I am softening the Hail by sending it through Moses so that you will continue to fight against Me and serve as a sign for all those who would deny Me. (Ba’eir Moshe – Vaeira #23)