Long ago on Mount Ōbai, in the middle of the night, the robe and the dharma of the Buddhas were genuinely transmitted upon the head of Hui Neng, our Sixth Ancestor. This was truly the authentic transmission of the passing on of the dharma and the passing on of the robe. . . A certain monk once asked the Sixth Ancestor, “Is the robe passed on to you on Mount Ōbai in the middle of the night one made of cotton, or one made of silk, or one made of taffeta? Pray, tell us, what on earth is it made of ?” 

 The Sixth Ancestor replied, “It is not cotton, or silk, or taffeta.” This was the way that the Highest Ancestor of Mount Sōkei put it. Keep in mind that the Buddha robe is not silk, or cotton, or some fine quality broadcloth. Those who vainly judge it to be silk, or cotton, or some fine-quality broadcloth are folks that slander the Buddha’s Dharma. - from Shobogenzo Den-e (The Transmission of the Robe)