John Calvin Commentary Exodus 12:42

"It is a night to be much observed unto Jehovah for bringing them out from the land of Egypt: this is that night of Jehovah, to be much observed of all the children of Israel throughout their generations." — Exodus 12:42 (ASV)

It is a night to be much observed. He shows that the Israelites have good reason to sacrifice to God with a solemn ceremony year by year forever, and to celebrate the memory of that night, and that the Passover was instituted as a token of their gratitude.

But this admonition was very useful so that the Israelites would retain the legitimate use of this solemn feast day, and so that it would not become a mere cold ceremony, as often happens; but rather that they might profitably, and for the advancement of their piety, engage in this emblem of their redemption.

At the same time, he teaches that this inestimable benefit was not to be celebrated for only one, two, or three generations. As long as the people remained, it was worthy of eternal remembrance, and, so that it might never be forgotten, the Passover was to be sacredly observed.

Moreover, we must note that the generations of the ancient people were brought to an end by the coming of Christ, because the shadows of the Law ceased when the state of the Church was renewed, and the Gentiles were gathered into the same body.