Śvetadvīpa-varṇana and Śāstra-pravartana (Śānti Parva 322)
आत्मना विदहितं दुःखमात्मना विहितं सुखम् | गर्भशय्यामुपादाय भुज्यते पौर्वदेहिकम्
bhīṣma uvāca | ātmanā vidhitaṃ duḥkham ātmanā vihitaṃ sukham | garbhaśayyām upādāya bhujyate paurvadehikam ||
Bhishma berkata: Duka ditata oleh diri sendiri, dan bahagia pun ditetapkan oleh diri sendiri. Begitu makhluk berjiwa mengambil peraduan rahim, ia mulai menikmati buah perbuatan yang dihimpun oleh tubuh terdahulu—yang matang menjadi suka dan duka.
भीष्म उवाच
That both suffering and happiness arise from one’s own actions: the self is the maker of its experience, and the results of past deeds (even from a previous embodiment) inevitably mature and are undergone.
In the Shanti Parva’s instruction on dharma and right understanding, Bhishma teaches Yudhishthira about karma and rebirth: the jīva, upon entering the womb, begins to experience the accumulated fruits of prior-life actions as pleasure and pain.