योगवासिष्ठः yogavāsiṣṭhaḥ - book-3, chapter-67, verse-44

चित्तं तन्मात्रमननं पश्यत्याशु स्वरूपवत् ।
एष सद्योऽनिललवप्रख्यः स्फुरति खान्तरे ॥ ४४ ॥

cittaṃ tanmātramananaṃ paśyatyāśu svarūpavat ,
eṣa sadyo'nilalavaprakhyaḥ sphurati khāntare 44

44. As Brahma the all extended and infinite soul, became the definite living soul at will; so the living spirit, became the mind by its volition afterwards.