John Calvin Commentary Exodus 12:24

"And ye shall observe this thing for an ordinance to thee and to thy sons for ever." — Exodus 12:24 (ASV)

And you shall observe this thing. He again repeats the precept concerning its annual celebration and expressly says that when they have come into the land, the recollection of their deliverance is to be revived yearly by this rite.

He adds, however, what he had not previously touched upon: that they should also teach their children, since, without the aid of this teaching, it would have been a meaningless and useless spectacle.

For doctrine may justly be called the life of sacraments, without which no vigor remains in them, so far are they from imparting any life to us.

So that the Passover would not be a lifeless ceremony, God in this place enjoins that it shall not be mute. For in these words, when your children shall say to you, Moses does not mean that they are to wait until their children inquire of their own accord and anticipate the zeal of their parents; rather, he only indicates the age when they are capable of being taught.

Yet, at the same time, he indirectly exhorts the children to teachableness, when their age allows them to understand what the Passover signifies, and enjoins them to inquire diligently into the use of the ceremony, so that religion may thus be handed down and may ever flourish among the people.

Since, then, the Paschal Lamb corresponds with the Holy Supper, we may gather from this that none can be duly admitted to receive it but those who are capable of being taught.