What does Exodus 12:24 mean?

Then Moses called for all the elders of Israel, and said to them, “Draw out, and take lambs according to your families, and kill the Passover.

You shall take a bunch of hyssop, and dip it in the blood that is in the basin, and strike the lintel and the two door posts with the blood that is in the basin; and none of you shall go out of the door of his house until the morning.

For Yahweh will pass through to strike the Egyptians; and when he sees the blood on the lintel, and on the two door posts, Yahweh will pass over the door, and will not allow the destroyer to come in to your houses to strike you.

It shall happen when you have come to the land which Yahweh will give you, according as he has promised, that you shall keep this service.

It will happen, when your children ask you, ‘What do you mean by this service?’

that you shall say, ‘It is the sacrifice of Yahweh’s Passover, who passed over the houses of the children of Israel in Egypt, when he struck the Egyptians, and spared our houses.’” The people bowed their heads and worshiped.