Mandukya Upanishad, verse 11


सुषुप्तस्थानः प्राज्ञो मकारस्तृतीया मात्रा मितेरपीतेर्वा मिनोति ह वा इदं सर्वमपीतिश्च भवति य एवं वेद ॥ ११ ॥

suṣuptasthānaḥ prājño makārastṛtīyā mātrā miterapītervā minoti ha vā idaṃ sarvamapītiśca bhavati ya evaṃ veda || 11 ||

11. Prājña whose sphere is deep sleep is M (म) the third part (letter) of Aum, because it is both the measure and that wherein all become one. One who knows this (identity of Prājña and M) is able to measure all (realise the real nature of the world) and also comprehends all within himself.

Shankara Bhashya (commentary)

One who is Prājña associated with deep sleep is M (म) the third sound (letter) of Aum. What is the common feature? It is thus explained. Here this is the common feature: The word Miti in the text means “measure”. As barley is measured by Prastha (a kind of measure), so also Viśva and Taijasa are, as it were, measured1 by Prājña during their evolution (utpātti) and involution (praḷaya) by their appearance from and disappearance into Prājña (deep sleep). Similarly2 after once finishing the utterance of Aum when it is re-uttered, the sounds (letters) A and U, as it were, merge into and emerge from M. Another common feature is described by the word “Apiteh” which means “becoming one”. When the word Aum is uttered the sounds (letters) A and U become3 one, as it were, in the last sound (letter) M. Similarly, Viśva and Taijasa become one (merge themselves) in Prājña in deep sleep. Therefore Prājña and the sound M are identical on account of this common basis that underlies them both. Now is described the merit of this knowledge. (One who knows this identity) comprehends all this, i.e., the real4 nature of the universe. Further he realises himself as the Ātman, the cause of the universe, i.e., Īśvara. The enumeration of these secondary5 merits is for the purpose of extolling the principal means (of knowledge).