Adbhutasagara 48.5

And Suśruta says:
"Death foretold by signs of death is indeed certain; but that, being pure, is averted
by brāhmaṇas, or by those devoted to elixirs, ascetic practices, and muttering [of mantras]."

The unfixed [sign of death] indicates untimely death. Untimely death is death caused by the major or minor planetary periods of cruel planets, and the like. And that can certainly be remedied by rites conferring welfare (svastyayana) and so forth.