Meaning of Mischief
In his Tafsir, As-Suddi said that Ibn `Abbas and Ibn Mas`ud commented,
[وَإِذَا قِيلَ لَهُمْ لاَ تُفْسِدُواْ فِى الأَرْضِ قَالُواْ إِنَّمَا نَحْنُ مُصْلِحُونَ ]
(And when it is said to them: "Do not make mischief on the earth,'' they say: "We are only peacemakers.'') "They are the hypocrites. As for,
[لاَ تُفْسِدُواْ فِى الأَرْضِ]
("Do not make mischief on the earth''), that is disbelief and acts of disobedience.'' Abu Ja`far said that Ar-Rabi` bin Anas said that Abu Al-`Aliyah said that Allah's statement,
[وَإِذَا قِيلَ لَهُمْ لاَ تُفْسِدُواْ فِى الأَرْضِ]
(And when it is said to them: "Do not make mischief on the earth,''), means, "Do not commit acts of disobedience on the earth. Their mischief is disobeying Allah, because whoever disobeys Allah on the earth, or commands that Allah be disobeyed, he has committed mischief on the earth. Peace on both the earth and in the heavens is ensured (and earned) through obedience (to Allah).'' Ar-Rabi` bin Anas and Qatadah said similarly.