Thou shall therefore keep the ordinance in his season,.... Not the ordinance of the phylacteries, as the Targum of Jonathan, but the ordinance of unleavened bread:
from year to year; every year successively, so long as in force, even unto the coming of the Messiah. It is in the Hebrew text, "from days to days" (c); that is, either year after year, as we understand it; or else the sense is, that the feast of unleavened bread, when the season was come for keeping it, was to be observed every day for seven days running.
(c) "a diebus in dies", V. L. Montanus, Munster, Vatablus, Drusius.

This ordinance the Israelites were to keep למועדהּ, "at its appointed time" (i.e., from the 15th to the 21st Abib), - "from days to days," i.e., as often as the days returned, therefore from year to year (cf. Judges 11:40; Judges 21:19; 1-Samuel 1:3; 1-Samuel 2:19).