तत एव च विस्तारं ब्रह्म सम्पद्यते तदा।।13.31।।
13.31 When one realizes that the state of diversity of living things is rooted in the One, and that their manifestation is also from That, then one becomes identified with Brahman.
13.31 When he perceives that the diversified modes of existence of all beings as men, divinities etc., are founded on the two principles of Prakrti and Purusa; when he perceives that their existence as divine, human, short, tall etc., is rooted in one common foundation, namely, in the Prakrti, and not in the self; when he sees that their expansion, i.e., the successive proliferaton into sons, grandsons and such varieties of beings, is from Prakrti alone - then he reaches the brahman. The meaning is that he attains the self devoid of limitations, in Its pure form of knowledge.
Yadaa bhootaprithagbhaavam ekastham anupashyati; Tata eva cha vistaaram brahma sampadyate tadaa.
yadā—when; bhūta—living entities; pṛithak-bhāvam—diverse variety; eka-stham—situated in the same place; anupaśhyati—see; tataḥ—thereafter; eva—indeed; cha—and; vistāram—born from; brahma—Brahman; sampadyate—(they) attain; tadā—then