Isaiah 64:4
2 As when fire ignites dry wood or fire makes water boil, let your adversaries know who you are, and may the nations shake at your presence! 3 When you performed awesome deeds that took us by surprise, you came down, and the mountains trembled before you. 4 Since ancient times no one has heard or perceived, no eye has seen any God besides you, who intervenes for those who wait for him. 5 You assist those who delight in doing what is right, who observe your commandments. Look, you were angry because we violated them continually. How then can we be saved? 6 We are all like one who is unclean, all our so-called righteous acts are like a menstrual rag in your sight. We all wither like a leaf; our sins carry us away like the wind.
1 Corinthians 2:9
7 Instead we speak the wisdom of God, hidden in a mystery, that God determined before the ages for our glory. 8 None of the rulers of this age understood it. If they had known it, they would not have crucified the Lord of glory. 9 But just as it is written, “Things that no eye has seen, or ear heard, or mind imagined, are the things God has prepared for those who love him.” 10 God has revealed these to us by the Spirit. For the Spirit searches all things, even the deep things of God. 11 For who among men knows the things of a man except the man’s spirit within him? So too, no one knows the things of God except the Spirit of God.
Notes and References
"... Where did Paul himself glean the borrowed material found in 1 Corinthians 2:9? The apostle introduces his material with a formulaic, “However, as it is written.” But what source or sources is he quoting? Paul normally uses such formulae while citing the Hebrew Scriptures. Nevertheless, no OT passage exactly parallels this text. Because of the lack of an exact OT parallel, scholars have posited various alternatives. First, many interpreters have proposed a “loose quotation” of Isaiah 64:4 (64:3 LXX), perhaps with further influence from Isaiah 65:17 (65:16 LXX) ... One does notice differences, such as the reverse order of ear and eye in Isaiah 64:4 as compared with 1 Corinthians 2:9. Nevertheless, according to Roy Ciampa and Brian Rosner, this reversal “does not rule out a link between the texts; such alterations were an accepted aspect of citation technique in antiquity.” One further notes that Isa 64:4 (64:3 LXX) refers to “those who wait [ὑπομένουσιν] for him,” while 1 Cor 2:9 refers to “those who love [ἀγαπῶσιν] him.” ..."
Hartog, Paul "1 Corinthians 2:9 in the Apostolic Fathers" in Bingham, D. Jeffrey, editor. Intertextuality in the Second Century (pp. 99-100) Brill, 2016