5.6 Tu, but, O mighty-armed one; sannyasah, renunciation, in the real sense; duhkham aptum, is hard to attain; ayogatah, without (Karma-) yoga. Munih, the meditative man-the word muni being derived in the sense of one who meditates on the real nature of God; yoga-yuktah, eipped with yoga, with Vedic Karma-yoga in the form of dedication to God without thought of results (for oneself); adhigacchati, attains; brahma, Brahman; na cirena, without delay, very ickly. Therefore it was said by Me, 'Karma-yoga excels'. [Karma-yoga leads to enlightenment through the stages of attenuation of attachment, withdrawal of the internal and external organs from their objects, and their inclination towards the indwelling Self. (Also see Commentary on 5.12).]
The monasticism under discussion is called Brahman because it leads to knowledge of the supreme Self, as stated in the Upanisad, 'Nyasa (monasticism) is Brahman. Brahman is verily the supreme' (Ma. Na. 21.2) Brahman means monasticism in the real sense, consisting in steadfastness to the knowledge of the supreme Self.