21 Then Moses called for all the elders of Israel, and said unto them, Draw out and take you a lamb according to your families, and kill the passover.
22 And ye shall take a bunch of hyssop, and dip it in the blood that is in the bason, and strike the lintel and the two side posts with the blood that is in the bason; and none of you shall go out at the door of his house until the morning.
23 For the LORD will pass through to smite the Egyptians; and when he seeth the blood upon the lintel, and on the two side posts, the LORD will pass over the door, and will not suffer the destroyer to come in unto your houses to smite you.
Seriously, you’d think that an omnipotent god could tell who his followers are.
But apparently not. It seems he had to go and have them mark their doors so that when he came around to slaughter the first born he’d skip their house. But now I wonder….how did he tell who was first born. I’d think that the culture difference would be a lot easier to tell than if a grown man was first born in his family.