Laudator Temporis Acti

Augustine, Confessions 1.2.2 (tr. Carolyn J.-B. Hammond, with her note):

Therefore since I too exist, why do I ask you to enter into me, when I would not exist but for your presence in me? After all, I am no longer in Hell; and yet there too you are present: for even if I go down into Hell, you are there.

quoniam itaque et ego sum, quid peto ut venias in me, qui non essem nisi esses in me? non enim ego iam inferi¹, et tamen etiam ibi es, nam etsi descendero in infernum, ades.

¹ (Reading inferi as locative) inferi S codd. Knöll Skut.: in infernis Maur: in <profundis> inferi Ver

James J. O'Donnell on inferi (electronic edition; some abbreviations expanded by me):

inferi C D G O1 S Knöll Skutella: inferis sum O2: in infernis Maurinorum editio: in <profundis> inferi Verheijen (cf. 3.6.11, 'in profunda inferi')

Interpretation is controversial:

• inferi as possessive genitive: Knauer 131, citing Thesaurus Linguae Latinae 7.1.1390.66; Pizzolato, Lectio I-II 20n65, comes to the same conclusion independently.
• as locative: Bibliothèque Augustinienne trans., 'je ne suis pas encore aux enfers.'
• nominative plural; Gibb-Montgomery: 'A. in fact does not mean merely "I am not in hell," but more boldly and pointedly "I am not, after all, hell; and even if I were, Thou wouldst still be in me—witness the Psalmist."' Pizzolato loc. cit. cites parallels for that construction (civ. 22.30, 'dies enim septimus etiam nos ipsi erimus'; conf. 13.2.3, 'fuimus . . . tenebrae' [Eph. 5.8]); and for the sense: inferi as place of the dead: vera el. 52.101, 'cavendi sunt ergo inferiores inferi, id est post hanc vitam poenae graviores'; qu. hept. 4.29 (on Num. 16.32: 'et descenderunt ipsi . . . viventes ad inferos'), 'notandum secundum locum terrenum dictos esse inferos, hoc est in inferioribus terrae partibus. varie quippe in scripturis et sub intellectu multiplici, sicut rerum de quibus agitur sensus exigit, nomen ponitur inferorum et maxime in mortuis hoc accipi solet.' Cf. also Gn. litt. 12.33.62, ep. 187.2.6.

Locative inferi seems unparalleled, but for a possible example of locative caeli see Gino Funaioli, "Der Lokativ und seine Auflösung," Archiv für lateinische Lexikographie und Grammatik 13 (1904) 301-372 (at 313):

Zuversichtlicher möchten wir caeli als Lokativ erklären bei Iulius Valer. Alex. 1, 8: nescius quae te impenderent humi, rimare ea quae caeli sunt; denn im griech. Originale heisst es: τὰ ἐπὶ γῆς μὴ ἐπιστάμενος τὰ ἐν οὐρανῷ ἐκζητεῖς. Im Lateinischen müssen freilich humi und in caelo im Interesse der Konzinnität ausgeglichen werden, entweder durch in humo, in caelo, wie Florus 2, 13, 91 schreibt in domo, in caelo, oder, was Valerius vorgezogen hat, durch Neubildung des Lokativs caeli, welcher sich leicht auch an terrae anlehnen konnte.