Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) says, concerning the statement of Allah Almighty "Fear Allah as He should be feared" [Surah Al Imran: 102]: "That is, that He be obeyed and not disobeyed, that He be thanked and not shown ingratitude, and that He be remembered and not forgotten."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8470