CC Madhya 18.190
‘sarvaiśvarya-pūrṇa teṅho — śyāma-kalevara
“The Koran accepts the fact that ultimately there is only one God. He is full of opulence, and His bodily complexion is blackish.
The revealed scripture of the Muslims is the Koran. There is one Muslim sampradāya known as the Sufis. The Sufis accept impersonalism, believing in the oneness of the living entity with the Absolute Truth. Their supreme slogan is “analahak.” The Sufi sampradāya was certainly derived from Śaṅkarācārya’s impersonalists.