Zohar 2:143b

Jewish Mysticism
This Song is the song that contains all of the Torah, the song in relation to which the upper and lower beings are aroused, the song that is in the pattern of the world above, which is the supernal Sabbath, the song on account of which the supernal, holy name is crowned. Therefore it is the holy of holies. Why? Because all of its words are in love and in the joy of everything.

Translated by Elliot Wolfson in “Asceticism and Eroticism in Medieval Jewish Philosophical and Mystical Exegesis of the Song of Songs.” In With Reverence for the Word- Medieval Scriptural Exegesis in Judaism, Christianity and Islam, 92-118. Edited by Jane Dammen McAuliffe, Barry D. Walfish, and Joseph W. Goering- Oxford and New York- Oxford University Press, 2003.