Karika 68

प्राप्ते शरीरभेदे चरितार्थत्वात्प्रधानविनिवृत्तौ। ऐकान्तिकमात्यन्तिकमुभयं कैवल्यमाप्नोति ॥६८॥

prāptē śarīrabhēdē caritārthatvātpradhānavinivr̥ttau। aikāntikamātyantikamubhayaṁ kaivalyamāpnōti ॥68॥

[प्राप्ते शरीर भेदे चरित-अर्थ-त्वात् प्रधान विनिवृत्तौ। ऐकान्तिकम् आत्यन्तिकम् उभयं कैवल्यम् आप्नोति॥
prāptē = on obtaining/ when time comes; śarīra = from the body; bhēdē = it escapes with a rupture; carita-artha-tvāt = having attained the goal; pradhāna = un-manifest material cause; vinivr̥ttau = having withdrawn; aikāntikam = certain / absolute; ātyantikam = final / imperishable; ubhayaṁ = both; kaivalyam = liberation; āpnōti = attains;]

When time comes, it escapes from the body with a rupture as unmanifest material cause, the pradhana, withdraws itself. Having reached the goal that is both absolute and imperishable, it attains liberation.

How the purusha obtains final liberation, the kaivalya, is described here.