5.21 Asakta-atma, with his heart, internal organ, unattached, bahya-sparsesu, to external objects-sparsah means objects that are contacted, viz sound etc.; bahya-sparsah means those things which are external (bahya) and are objects of contact; that person who thus has his heart unattached, who derives no happiness from objects; he vindati, gets that sukham, bliss; yat, which is; atmani, in the Self. Brahma-yoga-yukta-atma, with his heart absorbed in meditation on Brahman-meditation (yoga) on Brahman is brahma-yoga; one whose internal organ (atma) is absorbed in (yukta), engaged in, that meditation on Brahman is brahma-yoga-yukta-atma; he asnute, acires; aksayam, undecaying; sukham, Bliss.
So, he who cherishes undecaying happiness in the Self should withdraw the organs from the momentary happiness in external objects. This is the meaning.
For this reason also one should withdraw: