من جاء بالحسنة
Whosoever brings good,
meaning, on the Day of Resurrection,
فله خير منها
he shall have the better thereof;
meaning, the reward of Allah is better than the good deeds of His servant -- how can it not be, when Allah has multiplied it many times over. This is the position of generosity.
Then Allah says:
ومن جاء بالسيية فﻼ يجزى الذين عملوا السييات إﻻ ما كانوا يعملون
and whosoever brings evil, then those who do evil deeds will only be requited for what they used to do.
This is like the Ayah,
ومن جاء بالسيية فكبت وجوههم فى النار هل تجزون إﻻ ما كنتم تعملون
And whoever brings an evil deed, they will be cast down on their faces in the Fire. (And it will be said to them) "Are you being recompensed anything except what you used to do!'' (27: 90)
This is the position of generosity and justice