Sankaracarya's Vivekachudamani 461

अजो नित्यः शाश्वत इति ब्रूते श्रुतिरमोघवाक् ।

तदात्मना तिष्ठतोऽस्य कुतः प्रारब्धकल्पना ॥

ajo nityaḥ śāśvata iti brūte śrutiramoghavāk |

tadātmanā tiṣṭhato'sya kutaḥ prārabdhakalpanā ||

(Sankaracarya's Vivekachudamani 461)

The Self is "birthless, eternal and undecaying"---such is the infallible declaration of the Sruti. How can prarabdha be attributed to one abiding in the Self?

The self mentioned here is about the soul. Sankaracarya also mentioned Self as the Supreme Lord. The soul is part and parcel of the Supreme Lord. According to the Vedas, the soul has the quality of the Lord but not the quantity. Absolute the soul cannot take birth or die because it has the quality of the Lord. If a person surrendered and always in the service of the Lord, such a person's soul is not abode by past karmas. To avoid carrying past bad karmas we have to surrender to the Lord fully and avoid enjoying the material world.