לֹ֣א תֹסִ֗פוּ עַל־הַדָּבָר֙ אֲשֶׁ֤ר אָנֹכִי֙ מְצַוֶּ֣ה אֶתְכֶ֔ם וְלֹ֥א תִגְרְע֖וּ מִמֶּ֑נּוּ לִשְׁמֹ֗ר אֶת־מִצְוֺת֙ יְהוָ֣ה אֱלֹֽהֵיכֶ֔ם אֲשֶׁ֥ר אָנֹכִ֖י מְצַוֶּ֥ה אֶתְכֶֽם׃
No añadiréis á la palabra que yo os mando, ni disminuiréis de ella, para que guardéis los mandamientos de SEÑOR vuestro Dios que yo os ordeno.
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.