وَمِنْهُم مَّن يَلْمِزُكَ فِي الصَّدَقَاتِ فَإِنْ أُعْطُوا مِنْهَا رَضُوا وَإِن لَّمْ يُعْطَوْا مِنْهَا إِذَا هُمْ يَسْخَطُونَ
“There are some of them who are critical of your distribution of charity [O Prophet]. If they are given some of it they are pleased, but if not they are enraged.”
This is the asbab al-nuzul: this ayah addresses exactly the accusation of unfairness in distributing wealth that the post responds to ("Be fair in this money").