This ceremony depicts an integral part of the the plan of salvation. It was planned out well ahead of time — even before the physical creation and was given to the Israelites before they were able to implement it.
Wray
Should We Keep the New Moons?
Not Commanded
The simplest and most direct statement that can be made on this subject is:
How to Prepare for the Days of Unleavened Bread
The Days of Unleavened Bread begin and end with Holy Days. These annual high Sabbaths are holy convocations in which we are to come together as God has commanded (Leviticus 23:6-8). There are some things though that we need to do ahead of time in order to observe this holy time properly.