A commentary on the Prophetic Tradition 'Whoso knoweth himself knoweth his Lord' which has also been rendered 'He who knows the truth about himself surely knows God.' It is a statement of the fact of the essential unity of all existence, addressed to the most intimate consciousness.
The Andalusian author Shaykh Muhiyudeen ibn al'Arabi (1165 - 1240) is one of the greatest of Islamic saints and mystics. He says: 'This discourse is with God, not with other than God, and not with the blind. For he who attains this station knows that he is not other than God. And our discourse is with him who has resolution and energy in seeking to know himself in order to know God, and keeps fresh in his heart the image of his seeking and longing for union with God; and not with him who has neither aim nor end.' This short treatise can be read here. An audio mp3 file of the book can be downloaded here.