Mandukya Karika, verse 4.72


चित्तस्पन्दिकमेवेदं ग्राह्यग्राहकवद्द्वयम् ।
चित्तं निर्विषयं नित्यमसंगं तेन कीर्तितम् ॥ ७२ ॥

cittaspandikamevedaṃ grāhyagrāhakavaddvayam |
cittaṃ nirviṣayaṃ nityamasaṃgaṃ tena kīrtitam || 72 ||

72. This perceived world of duality, characterised by the subject-object relationship, is verily an act of the mind. The mind, again, (from the standpoint of Reality) is without touch with any object (as it is of the nature of Ātman). Hence it is declared to be eternal and unattached.

Shankara Bhashya (commentary)

The whole world of duality consisting of the subject and the object is, verily, an act of the mind. But from the standpoint of the Ultimate Reality, the mind, which is verily Ātman, is1 unrelated to any object. On account of the absence of relation (with any object), the mind is declared as eternal and unattached. The Śruti also says, “The Puruṣa is always free from relation.” That which perceives objects outside of it, is related to such objects. But the mind, having no such external object, is free from all relations.