A.T. Robertson Commentary 1 Corinthians 2:9

"but as it is written, Things which eye saw not, and ear heard not, And [which] entered not into the heart of man, Whatsoever things God prepared for them that love him." — 1 Corinthians 2:9 (ASV)

But as it is written (αλλα καθως γεγραπτα). Elliptical sentence like Rom 15:3 where γεγονεν (it has happened) can be supplied. It is not certain where Paul derives this quotation as Scripture. Origen thought it a quotation from the Apocalypse of Elias and Jerome finds it also in the Ascension of Isaiah. But these books appear to be post-Pauline, and Jerome denies that Paul obtained it from these late apocryphal books. Clement of Rome finds it in the LXX text of Isa 64:4 and cites it as a Christian saying. It is likely that Paul here combines freely Isa 64:4; 65:17; 52:15 in a sort of catena or free chain of quotations as he does in Ro 3:10-18. There is also an anacoluthon for α (which things) occurs as the direct object (accusative) with ειδεν (saw) and ηκουσαν (heard), but as the subject (nominative) with ανεβη (entered, second aorist active indicative of αναβαινω, to go up).

Whatsoever (οσα). A climax to the preceding relative clause (Findlay).

Prepared (ητοιμασεν). First aorist active indicative of ετοιμαζω. The only instance where Paul uses this verb of God, though it occurs of final glory (Luke 2:31; Matthew 20:23; Matthew 25:34; Hebrews 11:16) and of final misery (Matthew 25:41). But here undoubtedly the dominant idea is the present blessing to these who love God (1 Corinthians 1:5–7).

Heart (καρδιαν) here as in Ro 1:21 is more than emotion. The Gnostics used this passage to support their teaching of esoteric doctrine as Hegesippus shows. Lightfoot thinks that probably the apocryphal Ascension of Isaiah and Apocalypse of Elias were Gnostic and so quoted this passage of Paul to support their position. But the next verse shows that Paul uses it of what is now

revealed and made plain, not of mysteries still unknown.