Exodus 6:30

6:30 But Moses said before the Lord, “Since I speak with difficulty, why should Pharaoh listen to me?”

Exodus 6:12

6:12 But Moses replied to the Lord, “If the Israelites did not listen to me, then how will Pharaoh listen to me, since I speak with difficulty?”

Exodus 12:48

12:48 “When a foreigner lives with you and wants to observe the Passover to the Lord, all his males must be circumcised, and then he may approach and observe it, and he will be like one who is born in the land – but no uncircumcised person may eat of it.