Its triple mention serves to put the word in bold print. With its repetition the Holy Spirit stresses the togetherness of God and people, which is to say that the distance between God and humanity caused by our rebellion in Paradise (Genesis 3:23–24) has been fully overcome.
3 And I heard a loud voice from the throne saying, “Behold, the dwelling place of God is with man. He will dwell with them, and they will be his people, and God himself will be with them as their God.