Musar zu Jeschijahu 30:15

The reason that Kabbalists call only the emanation בינה Teshuvah, is twofold. Firstly, it is the place to which everything returns in the "great" Jubilee, i.e. the completion of the world's cycle of 7000 years. We are familiar with the basic concept from the Torah's יובל, the jubilee year legislation. The second reason is that a certain "inner spirit" reposes in that region. This is a spirit which comes directly from the emanation חכמה, which in turn is fed by the אין סוף, the ultimate of all causes, G–d's Essence, at all times. The philological origin of the expression תשובה, is derived from Isaiah 30,15, בשובה ונחת תושעון, "Through returning and rest will you be saved."