Devekut: Cleaving to the Divine
Devekut or D'vekut (“Clinging/Cleaving”) is the experience of mystical union with God, usually as an outcome of meditative prayer or spiritual exercises. The term originally expressed a more mundane notion of binding one’s self to God through good deeds and meticulous ritual practice,
For if you shall diligently keep all these commandments which I command you, to do them, to love the Lord your God, to walk in all his ways and to cleave unto Him...(Deut. 11:22; BT Ketubot 111b; Tanhuma Matot 1; Numbers Rabbah 22:11)
but it could also refer to the desire to draw close to God (BT Sanh. 64a, 65b; Sifre Shoftim 173; Gen. Rabbah 80:7). It is most intimately associated with various kinds of mystical ecstatic practices. This esoteric development of the term may reflect the sometimes ‘erotic’ aspect of the mystical experience. The first use of the term, after all, appears in Genesis, in association with the union of man and woman: a man... shall cleave unto his wife, and they shall become one flesh (Gen. 2:24).
Isaac the Blind is one of the earliest mystics to make extensive use of the term, mostly in the context of achieving fullest possible communion with God by focusing on the sefirot during prayer.
Moses Cordovero described a magical-theurgic dimension to devekut, in that the act of “clinging to God” can be used to influence the direction of divine forces in the higher worlds (Pardes Rimonim 75d). Chayyim Vital and Chasidism sometimes use it as term for beneficent spiritual possession, as exemplified by this passage:
And how is this mystery of cleaving performed? Let a righteous person stretch out on the grave of one of the tanna’im, or one of the prophets, and cleave with his lower soul to that of the tsaddiq, and with his spirit to his spirit. Then the tanna begins to speak with him as a person talks to a friend – and answers all that he ask, revealing to him all the mysteries of the Torah
In Chasidim, the term is often used to refer to a general attitude, often linked to cultivating the emotions of love and fear, of keeping one’s attention constantly focused toward God. In this way, devekut can be achieved while at prayer, studying, performing daily mitzvot.
Throughout most of it’s history, the term has not been used in a way akin to monastic mysticism or any other kind of denial of worldly life. Jewish mystics both affirm the need for everyone to pursue devekut and the need to be engaged with the world by teaching that the ordinary tasks of living are, with the right intention, the stepping stones to greater attachment with God (Or ha-Ganuz L’Tsaddikim, 73). However, this sense of a worldly devekut breaks down in some mystical systems, where it is explicitly described in terms of ‘separating’ oneself from the material world (Reshit Chochmah 4:23; Sha’ar ha-Kedushah 4:21).
 Origins of the Kabbalah, pp. 300-301.
 Spirit Possession in Judaism, pp. 257-304.
 Translation appears in Physician of the Soul, Healer of the Cosmos, p. 283.