Whatever his thought (at the time of death) with that he goes back to Prâna, and the Prâna, united with light, together with the self (the gîvâtmâ) leads on to the world, as deserved.

In plain words: Whatever a person is thinking at the moment of death, they carry that with them into Prana, the life-force. Prana, joined with the body's warmth and with the individual soul, then leads them to the world they have earned.