"The Zohar states that a kiss is the merging of one breath with another. Love begins with physical attraction. Then, as lovers begin communication, they begin to speak. As they get closer, they stop speaking and are merely aware of each other's breath. Finally, they come still closer, and their communication becomes a kiss, at which point they are actually in physical contact. At this moment, in the kiss, they are aware of each other's life force. Kissing is thus a natural consequence of increased intimacy in speech. The two mouths come closer and closer and progress from speech, to breath, to the kiss. Thus, there are four levels in the intimacy of love: physical attraction, speech, breath, and the kiss. These same levels exist in the relationship of a person with the Divine."
Quotation from Jewish Medidation: A Practical Guide by Rabbi Aryeh Kaplan (p. 139).
Does anyone know the source for this idea in the Zohar?