大毘盧遮那成佛經疏 14.6

14.6

次以左手猶如執蓮華形，梵天后印也（謂舒掌，以空風相捻其中指屈當掌內，圖中直申也）梵天無欲，反如人等身，云何言后耶？此是梵王明妃印相，義云妃也。

Next, with the left hand shaped as if holding a lotus, is the Brahmāṇī mudrā (that is, extend the palm, pinch the space and wind fingers together, and bend the middle finger inside the palm; in drawings it is extended straight). Brahmā is free of desire and appears in the form of a human male, so why say 'queen'? This is the mudrā form of the Vidyārājñī of King Brahmā; conceptually she is called a queen.