योगवासिष्ठः yogavāsiṣṭhaḥ - book-7, chapter-83, verse-18

अतः स कल्पान्तशिवो रुद्रो रौद्राकृतिर्द्रुतम् ।
यन्नृत्यति हि तद्विद्धि चिद्धनस्पन्दनं निजम् ॥ १८ ॥

ataḥ sa kalpāntaśivo rudro raudrākṛtirdrutam ,
yannṛtyati hi tadviddhi ciddhanaspandanaṃ nijam 18

18. Therefore the furious form of Rudra, which is assumed by the god Siva at the end of a kalpa; which is said to dance about at that time, is to be known as vibration of the divine intellect.