TSK
Treasury of Scripture Knowledge references in WEB.
I will set apart in that day the land of Goshen, in which my people dwell, that no swarms of flies shall be there; to the end you may know that I am Yahweh in the midst of the earth.
The blood shall be to you for a token on the houses where you are: and when I see the blood, I will pass over you, and there shall no plague be on you to destroy you, when I strike the land of Egypt.
Then you shall return and discern between the righteous and the wicked, between him who serves God and him who doesn't serve him.