Our sages said that Esau was going to receive Isaac’s blessing because Jacob did not have Kelim [vessels], but once Jacob received the hands of Esau, meaning Esau’s vessels of reception, and spoke with the voice of Jacob, it was a correction. Through the correction that Jacob made, he did not know him, for he had vessels of reception through the Hitkalelut [merging/mingling].
“The voice, the voice of Jacob, but the hands, the hands of Esau.” He did not know him because Jacob has the quality of a smooth man, having no deficiencies. For this reason, he had no Kelim in which to receive the blessings, since there is no light without a Kli [vessel].
“And Rebecca heard” and gave him the advice to borrow the clothing of the hairy one only so he would have Kelim to receive the blessing, and immediately after, return it.