Verse 3.2.9

स यो ह वै तत् परमं ब्रह्म वेद ब्रह्मैव भवति नास्याब्रह्मवित्कुले भवति ।
तरति शोकं तरति पाप्मानं गुहाग्रन्थिभ्यो विमुक्तोऽमृतो भवति ॥ ९ ॥

sa yo ha vai tat paramaṃ brahma veda brahmaiva bhavati nāsyābrahmavitkule bhavati |
tarati śokaṃ tarati pāpmānaṃ guhāgranthibhyo vimukto'mṛto bhavati || 9 ||

9. He who knows that highest Brahman becomes even Brahman; and in his line, none who knows not the Brahman will be born. He crosses grief and virtue and vice and being freed from the knot of the heart, becomes immortal.

Shankara’s Commentary:

Com.—It may he said that numerous obstacles are well known to exist in the attainment of good and that even the knower of Brahman may, therefore, be impeded either by some grief or other, or be made to take some other course by some other being, such as the Devas, reach some other after death and not reach Brahman. This cannot be; for all obstacles have already been removed by knowledge. Emancipation knows only the obstacle of ignorance and no other obstacle; because it is eternal and is being the Atman itself. Therefore, he in the world who knows that highest Brahman, as “I am directly that” does not take any other course. It is impossible even for the Devas to throw any obstacle in his attempt to reach the Brahman, because he becomes the Atman of all these; therefore he who knows the Brahman becomes even Brahman. Moreover in the line of this knower, there will not be born any who knows not the Brahman; again, he overcomes even during life the heart-burning caused by frustration of his many desires, crosses over karma known as vice and virtue, and being freed from “the knots of the heart” caused by ignorance, becomes immortal. It has already been said “the knot of the heart is untied, etc.”