|Pirkei Avot 5:4: Ramchal|
Ten miracles were performed for our ancestors in Egypt and ten at the Sea. Ten plagues did the Holy One, Blessed is He, bring upon the Egyptians in Egypt and ten at the Sea.
With ten trials did our ancestors test the Holy One, Blessed is He, in the Wilderness, as it is said, “They have tested Me these ten times and did not heed My voice (Numbers 14:22).” [Avot 5:4]
There are two types of damage caused during exile: the mixture of the mundane and in the holy, and the mixture of the holy into the mundane. Both of these were repaired during the Plague of Darkness, as the wicked died all the mundane that had been mixed into the holy was clarified and totally pushed away. As long as the mundane is mixed in with the holy it can grab onto some of the Illumination of the holy and derive continued existence. However, once it is pushed away entirely from the holy it remains in absolute darkness. This is the separation of the undesirable from the desirable.
When the Israelites took advantage of the Darkness to search for the valuable possessions of the Egyptians they were searching for the holy that had been mixed in with the mundane. They were separating the food, the desirable, from the undesirable.
The holy is A rumination. Anything which obscures God’s light is darkness. This is the secret of, “And the More separated between the light and between the dark.
The 10 miracles that were performed for our ancestors in Egypt were the separation of the holy from the mundane. The 10 plagues imposed on the Egyptians were the separation of the mundane from the holy.
Each time our ancestors tested God while in the Wilderness, they allowed the darkness to once again makes in with the Illumination.