Skandapurana 3.3.1.10

3.3.1.10

eṣa paṃcākṣaro maṃtro japtṝṇāṃ muktidāyakaḥ..
saṃsevyate muniśreṣṭhairaśeṣaiḥ siddhikāṃkṣibhiḥ..3.3.1.10
10 .. asyaivākṣaramāhātmyaṃ nālaṃ vaktuṃ caturmukhaḥ..

This five-syllabled mantra grants liberation to those who chant it; / it is constantly served by the best of sages, by all who desire accomplishments. / Even the four-faced [Brahmā] is not capable of reciting the greatness of its syllables. 10