From Rabbi Nachman Goldstein, Rav of Tcherin, and a leading disciple of Reb Noson, translated by Dovid Sears, "The Tree that Stands Beyond Space: Rebbe Nachman of Breslov on the Mystical Experience" (Breslov Research Institute), p. 83. (End notes have been omitted.)
Seclusion and Cleaving to God
The perfection of hitbodedut is to attain devekut -- to cleave to God until you become utterly subsumed within the Divine Oneness.
The word hitbodedut is a construct of badad, meaning either “seclusion" or "oneness," as in “They shall be one with one [bad v’bad, i.e., of equal weight]" (Rashi on Exodus 30:34). That is, you must become "one with God" to the extent that all sensory awareness ceases and the only reality you perceive is Godliness. This is the mystical meaning of the verse "There is nothing but God alone" (Deuteronomy 4:35).
This, too, is why the Torah calls Israel, "A people that dwells alone [badad]" (Numbers 23:9). The destiny of each Jew is to attain complete unification with God, without any intermediary (Zimrat HaAretz I, 52).