大毘盧遮那成佛經疏 20.7

20.7

第四赤如日暉，住三角中，右手執刀端坐，刀表利慧斷結也。如世日初出時，夜除晝現、暗盡明現，故取此色也。火神如是形色，光焰亦爾，身相端滿。如前住於三昧，作微怒形也。

The fourth is red like the radiance of the sun, dwelling within a triangle, holding a sword in his right hand, sitting upright; the sword represents sharp wisdom severing the fetters. Just as when the sun first rises in the world, night is removed and day appears, darkness is exhausted and light appears, this colour is adopted. The fire god has such form and colour, his blazing flames are likewise, and his bodily features are upright and full. As before, he abides in samādhi, displaying a slightly wrathful appearance.