Grimoire Book III, Chapter 1
The Book of Abramelin
The Knowledge and Conversation of the Holy Guardian Angel
The supreme operation: after the purification, the operator's Holy Guardian Angel manifests and reveals the operator's true name and purpose. All subsequent magical operations derive their authority from this relationship. Without it, the magician is a pretender.
Historical Note
This concept became central to Western esotericism through the Golden Dawn and Aleister Crowley, who considered the Knowledge and Conversation of the HGA the essential prerequisite for all magical work.