The true purport of his words, “Your actions alone will not save you”, “Actions alone will not cause one to enter Paradise”, can be further understood when it is realised that the reward of good deeds, multiplies manifold, only comes about by the beneficence and grace of Allah, Mighty and Magnificent. He recompenses a good deed tenfold to seven-hundred fold to whatever He wills. (Muslim) Were He to recompense a good deed with its like, in the same way that He does for an evil deed, good deeds would never have the strength to render void the evil deeds, and one would surely be destroyed.
Ibn Massud, may Allah be pleased with him, said, while describing good deeds, ‘If one is an ally (wali) of Allah, and there remain an atom’s weight of good [after mutual recompense], Allah would increase this manifold such that he enter Paradise through it. If he be one for whom misery is decreed, the Angel says, “My Lord, His good deeds have vanished yet many more people remain seeking [mutual recompense].” He will reply, “Take their evil deeds and add them to his evil deeds, then prepare for him a place of torment in the Fire!” (Abu Nu’aym, vol 4, p224)
Therefore it becomes clear that Allah multiplies the good deeds of those He wishes felicity for until they are able to pay off any penalties [from any who seek recompense]; and if, after all this, there remains even and atom’s weight worth of good, Allah will multiply this until He enters Paradise through it. All this by His grace and beneficence! However, whoever Allah has decreed misery for; his deeds will not be multiplied to the extent that they are able to pay off his penalties. Instead any good deeds performed by this latter person will only be multiplied ten-fold, apportioned amongst his creditors who will accept them all and yet still require further repayment for remaining injustices, and therefore their bad deeds are piled onto his, thereby causing him to enter the Fire. This, by His justice!
It is in this light that Yahya ibn Muadh said, ‘When He intends His grace, not a single evil deed remains for that person! When His justice is brought forth, not a single good deed remains for that person.’ (Abu Nu’aym, vol 10, p69)
It is also established in Bukhari and Muslim that the the Prophet, may Allah’s peace and blessings be upon him, said, “Whoever’s account is scrutinised will be destroyed” (Bukhari 6537, Muslim 2876/7227) in another narration, “…will be punished” (Bukhari 6536, Muslim 2876/7225 ) and in another, “… will be defeated.” (Hakim 8728)
Abdul Aziz ibn Abu Rawwad said, ‘Allah inspired Dawud, peace be upon him, saying, “Dawud, give glad tidings to the sinners and warn those who give charity.” Surprised, Dawud said, “My Lord, why should I give glad tidings to the sinners and warn those who give charity?” He relied, “Give glad tidings to the sinners that there is no sin that I find too grievous to forgive [even shirk if one repents from it] and warn those who give in charity that there is no servant upon whom I mete My justice and judgement except that he is destroyed.” (Abu Nu’aym, vol 8, p211)
Ibn Uyaynah said, ‘Scrutiny here means to undergo the evil of a thorough examination such that nothing is leftover.’ (Ibn Abi Shaybah 35644)
Ibn Yazid said, ‘The severe reckoning is that which contains no pardoning and the easy reckoning is that in which ones sins are forgiven and good deeds accepted.’ (Tabari 34351)
All of these narrations show that the servant cannot possibly succeed without forgiveness, mercy and the overlooking of his faults. They also show that when Allah enacts pure justice upon the servant, he will certainly be destroyed.
The Journey to Allah by Ibn Rajab Al-Hanbali Pages 26-30