Letters 57.9

We therefore come to this question,—whether the soul can be immortal. But be sure of this: if the soul survives the body after the body is crushed, the soul can in no wise be crushed out, precisely because it does not perish; for the rule of immortality never admits of exceptions, and nothing can harm that which is everlasting. Farewell.

Seneca, Letters to Lucilius 57.9, translated by Richard Mott Gummere