Exodus 12:17

ושמרתם את המצות AND YE SHALL WATCH THE UNLEAVENED BREAD that it shall not reach the stage of becoming leavened; hence the Rabbis said, if it (the dough) is rising (a sign that the leavening process is setting in) she (the woman kneading the dough) polishes it with cold water (i. e. she slaps the dough with hands dipped in cold water). Rabbi Josiah said: Do not read “את המַּצּוֹת”, the unleavened bread, but את הַמִּצְוֹת “[ye shall watch] the commandements” — just as we may not cause the unleavened bread to become leavened by letting the dough remain in its raw state too long so we may not let the commandment become “leavened” by waiting too long before we perform it; but if it (a commandment) comes to your hand, perform it immediately (Mekhilta). ושמרתם את היום הזה AND YE SHALL GUARD THIS DAY — against work, לדרתיכם חקת עולם THROUGHOUT YOUR GENERATIONS, AN ORDINANCE FOR EVER — Because the expressions, “[throughout your] generations”, and “an ordinance for ever” have not been mentioned in connection with the prohibition of work but only in reference to the celebration of the Festival (v. 14), it is therefore repeated here in order that you should not say: the prohibition, (v. 16) “no work shall be done”, was not spoken for future generations but for that generation alone to whom the words were addressed.

And you shall observe the commandment of unleavened bread; for on this very day have I brought your hosts out of the land of Miżrayim: therefore shall you observe this day in your generations by an ordinance for ever.

וּשְׁמַרְתֶּם֮ אֶת־הַמַּצּוֹת֒ כִּ֗י בְּעֶ֙צֶם֙ הַיּ֣וֹם הַזֶּ֔ה הוֹצֵ֥אתִי אֶת־צִבְאוֹתֵיכֶ֖ם מֵאֶ֣רֶץ מִצְרָ֑יִם וּשְׁמַרְתֶּ֞ם אֶת־הַיּ֥וֹם הַזֶּ֛ה לְדֹרֹתֵיכֶ֖ם חֻקַּ֥ת עוֹלָֽם׃