'Unclean' in the Bible

And Moses, answering the Lord, said, See, the children of Israel will not give ear to me; how then will Pharaoh give ear to me, whose lips are unclean?

And Moses said to the Lord, My lips are unclean; how is it possible that Pharaoh will give me a hearing?

And if you make me an altar of stone do not make it of cut stones: for the touch of an instrument will make it unclean.