Dzogchen / As it is [4]

~Tulku Urgyen Rinpoche

Remember, 'nirvana' refers to the Body, Speech and Mind of all the awakened ones. Body is the abiding essence, Speech is the vividly present nature, and Mind is the radiant capacity. These three, the Body, Speech and Mind of all buddhas, are also known as the three vajras.

This buddha nature is present just as the shining sun is present in the sky. It is indivisible from the three vajras of the awakened state, which do not perish or change. Vajra Body is the unchanging quality, vajra Speech is the unceasing quality and vajra Mind is the undeluded, unmistaken quality. So, the buddha nature or dharmadhatu is the three vajras; at the same time, its expression manifests as the deluded body, speech and mind of all beings. 

In the normal sense of the word, 'body' refers to something perishable composed of flesh and blood. 'Speech' refers to intermittent utterances that come and go and eventually perish. And 'mind' refers to thought states and emotions that come and go, come and go, under the power of dualistic attitude, like beads on a rosary. These mental states are also transient.