Wherein they abide eternally; [it is] the promise of Allah [which is] (31:9)

Almuntakhab Fi Tafsir Alquran Alkarim

wherein they will have passed through nature to Eternity as promised by Allah Whose promise is the truth personified. He is AL-Aziz (the Almighty) and AL- Hakim (the Source of Wisdom and wise mysterious dispensations)

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(31:9) They shall abide in them forever. This is Allah's promise that shall come true. He is the Most Powerful, the Most Wise. *11

Wherein they abide eternally; [it is] the promise of Allah [which is] meaning

*11) That is, "Nothing can withhold Him from fulfilling His promise, and whatever He does, He does strictly according to the demands of wisdom and justice. The object of mentioning these two attributes of Allaln after saying: This 'is a true promise of AIIah", is to stress that AIIah neither violates His promise wilfully nor is there in this universe any such power as can prevent Him from fulfilling His promise. Therefore, there can be no chance that one may not receive what AIIah has promised to give as a reward for faith and righteous deeds. Moreover, Allah's open promise to bestow this reward is wholly based on His wisdom and His justice. He does not misjudge: it cannot be that He may deprive a deserving person of his reward, and reward a non-deserving one instead. The people characterised by taste faith and righteous deeds indeed deserve this reward and AIIah will bestow this on them only."
 

Wherein they abide eternally; [it is] the promise of Allah [which is] meaning in Urdu

جن میں وہ ہمیشہ رہیں گے یہ اللہ کا پختہ وعدہ ہے اور وہ زبردست اور حکیم ہے