Here are some options:
General greetings:
* Nau mai, haere mai: This is a very common greeting used to welcome someone, which can be translated as "Welcome, come in." It's appropriate for a general welcome back.
* Tena koe, kua hoki mai koe: This translates to "Greetings, you have returned." This is a more formal way to say "welcome back" and emphasizes the return.
Specific greetings:
* Nga mihi nui ki te hoki mai: This translates to "Many thanks for returning." It's a more formal way to welcome back someone after a long absence.
* Ata mārie, kua hoki mai koe: This translates to "Peace be with you, you have returned." This is a more spiritual greeting that could be used to welcome someone back from a journey or a difficult period.
* Mauri ora! Kua hoki mai koe! This translates to "Life force! You have returned!" It's a more enthusiastic and celebratory way to welcome someone back.
The best way to choose the right phrase is to consider the context and the relationship with the person you are welcoming back.