So Moses told the Israelites to celebrate the Passover,
Then Moses summoned all the elders of Israel and said to them, “Go at once and select the animals for your families and slaughter the Passover lamb.
Celebrate it at the appointed time, at twilight on the fourteenth day of this month, in accordance with all its rules and regulations.”
and they did so in the Desert of Sinai at twilight on the fourteenth day of the first month. The Israelites did everything just as the Lord commanded Moses.