קַדֶּשׁ־לִ֨י כָל־בְּכ֜וֹר פֶּ֤טֶר כָּל־רֶ֙חֶם֙ בִּבְנֵ֣י יִשְׂרָאֵ֔ל בָּאָדָ֖ם וּבַבְּהֵמָ֑ה לִ֖י הֽוּא׃
Santifícame todo primogénito, cualquiera que abre matriz entre los hijos de Israel, así de los hombres como de los animales: mío es.
Zohar
The first words that appear in the Tefilin read, "Sanctify to Me all the firstborn (Heb. קַדֶּשׁ לִי...)" (Exodus 13:2). This corresponds to Yud, which is holiness - which is the firstborn of all the supernal sanctities. These are "whatever opens the womb" (Exodus 13:12) by that narrow line that descends from the Yud, which opens the womb to bring forth proper fruit and seeds. This is the supernal holiness.