The Passover is a God's feast have to engrave on our souls.

It is a spiritual compass that we can return to him even when we lose God.

Furthermore, God said, "I will put my law in their hearts".

So, who are they? They are God's children and it means his children keep his law.

Therefore, the Passover also serves to distinguishing his children, because it is God's law.
[Jeremiah 31:31–33]
“The days are coming,” declares the LORD, “when I will make a new covenant
with the people of Israel and with the people of Judah. . . . This is the covenant I will make
with the people of Israel after that time,” declares the LORD. “I will put my law in their minds
and write it on their hearts. I will be their God, and they will be my people.”