大毘盧遮那成佛經疏 20.6

20.6

第三火尊名為風燥。從風所生，是為風子，形燥黑也。此謂內色黑而外加燥形，如上塗灰等也。此尊處風輪中，即半月形也。亦作端坐三昧之形。謂行人初發菩提心雖欲進行，而無始來妄惑煩惱根本未除，數來牽破觀心而加暗𦿔，謂作此法也。風是不住義，又如世間風能壞重雲。此不住之火亦如是，能散壞諸障也。此尊坐風壇中，手執帛，去頭三五寸，兩頭執之，如天衣形，其色青也（此是表風義也。更問）。此是阿毘闍嚕迦法，亦有內外二法。

The third fire deity is named Wind-Drying. Born from the wind, he is the son of the wind, his form dry and black. This means that his internal colour is black, with an externally added dry appearance, like being smeared with ashes as mentioned above. This deity resides within a wind-wheel, which is in the shape of a half-moon. He also assumes the form of sitting upright in samādhi. This means that although a practitioner initially generates the bodhicitta and wishes to make progress, the roots of beginningless delusive confusion and afflictions have not yet been eliminated, repeatedly arising to drag down and break the contemplative mind, adding darkness and gloom; thus this rite is performed. Wind has the meaning of not abiding; furthermore, just as worldly wind can dispel dense clouds, so too this non-abiding fire can scatter and destroy all obstacles. This deity sits in a wind altar, his hands holding a silk cloth three to five inches away from his head, grasping both ends like the shape of heavenly robes, its colour being blue-green (this represents the meaning of wind; to be inquired further). This is an abhicāraka rite, which also has two methods: internal and external.