The Targum Pseudo-Jonathan preserves one of the most quoted lines in all of Genesis. Isaac, blind and suspicious, draws Jacob near, touches him, and says, "This voice is the voice of Jakob, nevertheless the feeling of the hands is as the feeling of the hands of Esau" (Genesis 27:22).
Voice of one brother. Hands of another. The patriarch is holding two sons in a single moment and cannot tell them apart.
The two signs of a Jew
The rabbis read this verse as a lasting prophecy. Ha-kol kol Yaakov, v'ha-yadayim y'dei Esav — the voice is Jacob's, the hands are Esau's. The Midrash in Bereshit Rabbah 65:20 teaches that Jacob's people will always be recognized by the voice — the voice of Torah, of prayer, of study in the beit midrash. When that voice is strong, Esau's hands cannot harm us. When the voice goes silent, the hands begin their work.
It is a staggering reading. Jewish history, the rabbis are saying, is shaped by whether the synagogues are humming or silent. The schools of Torah and the sound of prayer are not ornaments. They are the protective force.
Isaac's moment of doubt
Pseudo-Jonathan does not smooth over Isaac's uncertainty. The patriarch hears the voice and hesitates. Some sages taught that this hesitation was providential — Isaac was given every chance to stop, and yet the blessing flowed to Jacob anyway, because Heaven had decided. The mismatch between voice and hand was the seam through which the Divine Will reached the correct son.
The takeaway: your voice is your signature. In the Targum's reading, every time a Jew opens a sefer or begins to daven, the world is reshaped around that sound.