18. Quran verse and the related hadith:

السلام عليكم ورحمة الله وبركاتة

بِسْمِ ٱللَّٰهِ ٱلرَّحْمَٰنِٱلرَّحِيمِ

اَ لْيَوْمَ تُجْزٰى كُلُّ نَـفْسٍ بِمَا كَسَبَتْ  لَا ظُلْمَ الْيَوْمَ  اِنَّ اللّٰهَ سَرِيْعُ الْحِسَابِ

This Day every soul will be recompensed for what it earned. No injustice today! Indeed, Allāh is swift in account. [Al Quran, 40:17]

Here Allah tells us of His justice when He judges between His creation; He does not do even a speck of dust's weight of injustice, whether it be for good or for evil. For every good deed He gives a tenfold reward and for every bad deed He gives recompense of one bad deed. Allah says:

Abu Dharr (May Allah be pleased with him) said:

The Prophet (ﷺ) said, "Allah, the Exalted, and Glorious, said; 'O My slaves! I have prohibited Myself injustice; and have made oppression unlawful for you, so do not oppress one another.

O My slaves! All of you are liable to err except the one whom I guide on the Right Path, so seek guidance from Me so that I will guide you to the Right Path. 

O My slaves! All of you are hungry except the one whom I feed, so ask food from Me, I will feed you. 

O My slaves! All of you are naked except those whom I clothe, so ask clothing of Me and I shall clothe you. 

O My slaves! You commit sins night and day and I forgive all sins, so seek My forgiveness and I shall forgive you. 

O My slaves! You can neither do Me any harm nor can you do Me any good. 

O My slaves! Were the first of you and the last of you, the human of you and jinn of you to be as pious as the most pious heart of any man of you, that would not increase My domain a thing. 

O My slaves! Were the first of you, and the last of you, the human of you and the jinn of you to be as wicked as the most wicked heart of any man of you, that would not decrease My domain in a thing. 

O My slaves! Were the first of you and the last of you, the human of you and the jinn of you to stand in one place and make a request of Me, and were I to give everyone what he requested, that would not decrease what I have, any more than a needle decrease the sea if put into it. 

O My slaves! It is but your deeds that I reckon for you and then recompense you for, so let him who finds good (i.e., in the Hereafter) praise Allah and let him who finds other than that blame no one but himself." [Riyad as-Salihin 111 and Ṣaḥīḥ Muslim 2577a]

Truly, Allah is swift in reckoning. means, He will bring all His creation to account as if He is bringing just one person to account. He says in the following aayath: ‘The creation of you all and the resurrection of you all are only as a single person’ (31: 28). ‘And Our commandment is but one as the twinkling of an eye’ (54:50).

الحمدلله