यदा सर्वे प्रमुच्यन्ते कामा येऽस्य हृदि श्रिताः । अथ मर्त्यो'मृतो भवत्यत्र ब्रह्म समश्नुते ॥ १४ ॥
yadā sarve pramucyante kāmā ye'sya hṛdi śritāḥ | atha martyo'mṛto bhavatyatra brahma samaśnute |
When all desires clinging to the heart of one fall off, then the mortal becomes immortal and here attains Brahman.(Katha Up 2.3.14)
In this verse who is becoming immortal?
Because souls is immortal and was immortal and the body is mortal.
BG 2.20: The soul is neither born, nor does it ever die; nor having once existed, does it ever cease to be. The soul is without birth, eternal, immortal, and ageless. It is not destroyed when the body is destroyed.
Soul was never mortal but this verse is say he will become immortal("then the mortal becomes immortal"), so who will become immortal .
Is it the body because it is mortal and subjected to death?