Seneca, Letters to Lucilius
83.1 (tr. Richard M. Gummere):
At any rate, it is thus that we should live,—as if we lived in plain sight of all men; and it is thus that we should think,—as if there were someone who could look into our inmost souls; and there is one who can so look. For what avails it that something is hidden from man? Nothing is shut off from the sight of God.
sic certe vivendum est, tamquam in conspectu vivamus; sic cogitandum, tamquam aliquis in pectus intimum introspicere possit; et potest. quid enim prodest ab homine aliquid esse secretum? nihil deo clusum est.