But Moses said to YHWH, “Behold, the people of Israel have not listened to me. How then shall Pharaoh listen to me, for I am of uncircumcised lips?”
#exodus 6:12 ESV

The use of "uncircumcised lips" shows that the ancient Hebrews always knew circumcision is only an outward sign of an inward condition. This wasn't an idea invented in the first century or even by the prophets of Israel. It predates them all.