Parshas Hashavua
Devarim 11:31
Ramban: You shall possess it and shall (command) settle in it.
In Parshas מסעי (Bamidbar 33:53) there is a similar Pasuk.
מחלוקת רש"י ורמב"ן
רש"י explains that the Mitzvah is to conquer and rid the other nations living in the land and by doing so you will have the capability to settle in Eretz Yisroel.
1) According to רש"י, there is no such Mitzvah of ישוב א"י.
2) The רמב"ן argues and holds that וישבתם בה is a מצוות עשה דאורייתא that is applicable even בזמן הזה.
The ויואל משה* writes that מצוות ישוב א"י is only for those who are יראי שמים and doing it 100% לשם שמים.
In Contrast
The ספר אם הבנים שמחה (פתיחה)* argues that anyone who builds or develops Eretz Yisroel—even רשעים גמורים with no intention of fulfilling the mitzvah—still fulfills it. Their personal motives do not negate the objective mitzvah.
A proof that can't be disputed from the גמרא סנהדרין ק"ח, which asks why King Omri merited three generations of kingship.
Because he built a city in Eretz Yisroel.
(Shomron)
Despite being a רשע ועובד ע"ז king, and having built the city just for his own ego, Omri was rewarded for adding a city to the Land.
Since reward implies Mitzvah fulfillment, it follows that even action done by רשעים for ego or personal gain שלא לשם שמים can still constitute קיום מצות ישוב א"י. (Otherwise, why was he rewarded?)