Laghustutih (vrittisameta) 40

40

iti śrībhagavadgītoktanītyā prakṛtiratha hasaṃjñā bhaved vyāpya
viśvamityācāryoktanītyā ca dvandvasamāsatvaṃ napuṃskatvamekatvaṃ ca
prāptākārahakāravigraho'haṃśabdo'napāyī pareti mahāmantra iti ca prasiddho
vākśabdena gṛhyate tadatmānamevāvedahaṃ brahmāsmīti śruteḥ

and according to the rule stated by the teacher: “Now, having pervaded the universe, it is designated as ‘ha’,” the word “ahaṃ,” whose form is composed of the letters ‘a’ and ‘ha’ having attained the state of a dvandva compound, neuter gender, and singular number, [and which is] renowned as the imperishable, Parā, and the great mantra, is signified by the word “speech” (vāc), because of the Upaniṣadic text: “It knew itself alone: ‘I am Brahman.’”