大毘盧遮那成佛經疏 10.44

10.44

次金剛無勝三昧。更無等比，名為無勝。由現覺諸佛金剛之體，能持諸佛智故，名執金剛。歸命諸金剛者，金剛即諸佛智印也，即諸佛之別名也。

Next is the Vajrāparājita Samādhi. Having no equal is called 'invincible' (aparājita). Because of directly awakening to the vajra-essence of all Buddhas and being able to hold the wisdom of all Buddhas, he is called Vajradhara. Taking refuge in all vajras: the vajra is the wisdom seal of all Buddhas, an alternative name for all Buddhas.