[It will be said], "This is what you were promised – for every returner and keeper
'awaabin hafiiZ has been translated in the above as "returner and keeper." Imaam al-Tabari mentions the different understandings of the scholars of Tafsiir from the Salaf regarding hafiiZ and then concludes by saying:
وأولى الأقوال في ذلك بالصواب أن يقال: إن الله تعالى ذكره وصف هذا التائب الأوّاب بأنه حفيظ, ولم يخصّ به على حفظ نوع من أنواع الطاعات دون نوع, فالواجب أن يعمّ كما عمّ جلّ ثناؤه, فيقال: هو حفيظ لكلّ ما قرّبه إلى ربه من الفرائض والطاعات والذنوب التي سلَفت منه للتوبة منها والاستغفار
The saying which is closest to being right is that it be said that Allaah has not specified hafiiZ [keepr] for any particular category of obedience from any other. Thus, it is obligatory that we understand the word in its general meaning as Allaah has not specified it.
And it means to keep steadfast on every thing which brings one close to Allaah such as performing the prescribed obligations and all forms of obedience and repenting and asking forgiveness from sins which one has done.