Explained in the fifth verse (35) is the detail of the ` painful punishment' referred to at the end of verse 34. There, it has been said: يَوْمَ يُحْمَىٰ عَلَيْهَا فِي نَارِ جَهَنَّمَ فَتُكْوَىٰ بِهَا جِبَاهُهُمْ وَجُنُوبُهُمْ وَظُهُورُهُمْ ۖ هَـٰذَا مَا كَنَزْتُمْ لِأَنفُسِكُمْ فَذُوقُوا مَا كُنتُمْ تَكْنِزُونَ ﴿35﴾(on the day it will be heated up in the fire of Jahannam, then their foreheads and their sides and their backs shall be branded with it: "This is what you had accumulated for yourselves. So, taste what you have been accumulating". It means that this ` painful punishment' will be for those who do not pay Zakah. It will come on a day when the gold and silver accumulated by them will be heated up in the Fire of Jahannam.
Then, their foreheads, sides and backs shall be branded with it, and they shall be told, as a sort of verbal punishment, that it was what they had accumulated for themselves, and in consequence, they better have a taste of what they had accumulated. The return of a deed is the deed itself. That which was accumulated illegally or that which was accumulated legally but without having paid its Zakah ultimately became, by itself, the punishment of these people.
In this verse, mention has been made of branding foreheads, sides and backs. Either it means the whole body or these three parts have been particularized for the reason that a miser who does not like to spend his wealth in the way of Allah would usually greet a needy visitor looking for charity or Zakah with a forehead all wrinkled with distaste. After that, when to avoid him, he tries to turn away to the right or the left side. And if the needy person still persists, he would turn his back on him. Perhaps, the forehead, the sides and the back were thus particularized for this punishment.