What you wrote reminds me a lot of the theme in Petrine literature, especially the following passage in the Kerygma Petrou:
"For we find in the Scriptures, as the Lord says: 'Behold, I make with you a new covenant, not as I made with your fathers in Mount Horeb'. He made a new covenant with us; for what belonged to the Greeks and Jews is old. But we, who worship him in a new way, in the third form, are Christians. For clearly, as I think, he showed that the one and only God was known by the Greeks in a Gentile way, by the Jews Judaically, and in a new and spiritual way to us" (Kerygma Petrou, Clem. Alex. Stromata 6.5)
See also the parallel in 1 Peter 2:9 and the Valentinian Gospel of Philip 102b.