לֹ֣א תֹסִ֗פוּ עַל־הַדָּבָר֙ אֲשֶׁ֤ר אָנֹכִי֙ מְצַוֶּ֣ה אֶתְכֶ֔ם וְלֹ֥א תִגְרְע֖וּ מִמֶּ֑נּוּ לִשְׁמֹ֗ר אֶת־מִצְוֺת֙ יְהוָ֣ה אֱלֹֽהֵיכֶ֔ם אֲשֶׁ֥ר אָנֹכִ֖י מְצַוֶּ֥ה אֶתְכֶֽם׃
N’ajoutez rien à ce que je vous prescris et n’en retranchez rien, de manière à observer les commandements de l’Éternel, votre Dieu, tels que je vous les prescris.
Mishnah Eruvin
One who finds tefillin should bring them in one pair at a time. Rabban Gamaliel says: two pairs at a time. To what does this apply? To old ones but in the case of new ones he is exempt. If he found them arranged in a set or in bundles he shall wait by them until it is dark and then bring them in. In a time of danger, he should cover them and walk away.