In Exodus 6:12, being uncircumcised in lips signifies that he is impure in relation to things doctrinal. (Arcana Coelestia 7225)

In Ezekiel 44:9, it signifies one who has not been purified from the evils of merely natural love, and so is uncharitable. (Doctrine Regarding Faith 54)

'Uncircumcised in lips,' as in Exodus 6:30, signifies being impure regarding doctrine. 'Circumcision' represented purification from filthy loves, that is, the loves of self and the world. So people who were not circumcised, or 'the uncircumcised,' represent people who were not purified from these loves, so they were impure. 'Lips' denote these aspects of doctrine, so 'uncircumcised in lips' signifies being impure regarding these aspects of doctrine, for 'uncircumcised' refers both to doctrine and of life.

The ear is also said to be 'uncircumcised' in Jeremiah 6:10, and 'the heart' in Jeremiah 9:26, Ezekiel 44:7, 9, and Leviticus 26:41. In these passages it is clear that 'uncircumcised' denotes impurity. Because anything impure is from the impure loves, 'uncircumcised' signifies an impediment to the influx of good and truth. Wherever these loves are, inflowing good and truth is extinguished, because they are opposites like heaven and hell. 'The uncircumcised ears' are disobedience, and 'the uncircumcised heart,' the rejection of good and truth. This is especially the case when these loves have fortified themselves with falsity like a wall.

Moses calls himself 'uncircumcised in lips' because he stuttered for the sake of the internal sense. This was to signify that people who are in falsities, represented by Pharaoh, would not heed what was said to them from divine law, because people caught up in falsities call the truths of the divine law falsities, and call falsities opposed to divine law truths, because they are totally the opposite. So they perceive the truths of doctrine as impure.