Sir Richard C. Jebb, Commentary on Sophocles: Oedipus at Colonus

ἢ τὸ νερτέρων γῆς βάθρον, the nether world on which the upper world rests. “γῆς βάθρον”, earth's firm floor, rocky base: cp. Milton, “"Hymn on the Nativity,"” And cast the dark foundations deep. So Ai. 860 “ἑστίας βάθρον” is the ground on which the home stands.

ἀλύπητον, the MS. reading, is incomparably better than the variant ἀλάμπετον, which I believe to have been merely one of those conjectures in which the old transcribers and commentators sometimes indulged. By ἀλύπητον the poet meant, “"without pain"” (to Oed.); though it does not follow that he used the word with definite consciousness of an active sense. Cp. Ph. 687 “ἀμφιπλήκτων ῥοθίων”, the billows that beat around him: O. T. 969 “ἄψαυστος”, “"not touching,"” etc. ( ib. 885 “ἀφόβητος”, “"not fearing,"” is not properly similar, since “ἐφοβήθην” was deponent). Plat. Legg. 958E “τὰ τῶν τετελευτηκότων σώματα μάλιστα ἀλυπήτως τοῖς ζῶσι... κρύπτειν”, to bury the dead with least annoyance to the living. The passive sense, “"not pained,"”—i.e., where all earthly pain is over,—seems less suitable. Pollux 3. 98 says, “Πλάτων δὲ καὶ ἀλύπητος ἔχει, ὥσπερ καὶ Σοφοκλῆς ἀλύπητον”: where, since Plat. has the word only in the place just cited, “ἀλύπητος” should perh. be “ἀλυπήτως”. The second ref. seems to indicate this passage, rather than Tr. 168 “ζῆν ἀλυπήτῳ βίῳ”, and, if so, proves the existence of the reading as early at least as c. 160 A.D.

ἀλάμπετον (instead of “ἀλαμπές”) is not attested for the classical age, though it occurs in later poetry (Anthol. P. 9. 540, etc.), as does also a subst. “λαμπέτης”.