Keeping the Statute Tefillin by Day and Fixing the Calendar

"And you shall keep this statute at its appointed time" (Exodus 13:10). Since it says "and it shall be a sign for you on your hand," I might understand that even minors are included; Scripture says "and you shall keep" — I spoke only of one who has the awareness to keep [guard] it. From here they said: a child who knows how to guard his tefillin is obligated in tefillin. Another interpretation: "and you shall keep this statute at its appointed time." Rabbi Eliezer says: this is the statute of the Passover. Rabbi Akiva says: this is the statute of tefillin. One might think tefillin should be worn at night as by day. It would follow by reasoning: if the mezuzah, which does not apply to seafarers and desert travelers, applies at night as by day, then tefillin, which does apply to seafarers and desert travelers, should surely apply at night as by day. Scripture therefore says "from days [to days]" — excluding nights. One might think tefillin should be worn on festivals and Sabbaths. Scripture says "from days," and not all days. Rabbi Akiva says: tefillin should not be worn on Sabbaths and festivals, for Scripture says "a sign on your hand" — Sabbaths and festivals are excluded, since they are themselves a sign. One might think he need not inspect his tefillin from time to time; from here they said a person must inspect his tefillin once in twelve months. It says here "from days [to days]" and it says elsewhere, "for a full year [days] shall be its right of redemption" (Leviticus 25:29): just as there it is twelve months, so here it is twelve months — the words of the House of Hillel. The House of Shammai say: he need never inspect them. And so Shammai used to say: these are the tefillin of my mother's father. "At its appointed time" — this teaches that one intercalates the year only in the period close to the appointed festival [the spring]. And how do we know that one declares the leap-month only by day, and sanctifies the new moon only by day? Scripture says "from days to days." And how do we know that one fixes the months and intercalates the years only in the Land of Israel? Scripture says "and you shall keep this statute at its appointed time," and adjacent to it, "and it shall be when the LORD brings you in" — from here that one does not intercalate years or fix months outside the Land, but only in the Land of Israel and in the cities of Judah, where the Divine Presence dwells, as it says, "to His dwelling shall you seek" (Deuteronomy 12:5). [And if a court went out near the border of the Land and left none equal to it within the Land, it is permitted to fix months and intercalate years outside the Land; but if it became known that a sage equal to it had arisen in the Land of Israel, and all the more so one greater than it, then it is forbidden to intercalate or fix outside the Land.]