Question: The majority of people are not Muslims. Since all non-Muslims will go to Jahannam [Hell], then how can it be said that Allah’s mercy has surpassed His wrath?
ANSWER
Hadrat Imâm-i Rabbânî declares:
Allahu ta’âlâ Himself is hostile against disbelievers and kufr [disbelief]. All the idols they worship and those who worship them are the enemies of Allahu ta’âlâ Himself. Eternal torment in Hell is the punishment for this disbelief. But other kinds of sins are not so. Allah’s enmity towards them is not from His own Self but from His Attributes. Allah’s wrath and anger against sinners does not originate from His own wrath but from His Attribute wrath. His tormenting and abhorring them is always through His deeds and attributes. It is for this reason that sinners will not remain in Hell eternally. Since Allah’s enmity against disbelief and disbelievers is from His own Self, His attributes mercy and compassion will not cancel the enmity of His own Self. Enmity of the Self is more powerful than the mercy of the Attribute. What is done through the Attribute cannot change what is done by the Self.

It is purported in a hadîth-i qudsî;
(Sabakat rahmati ‘alâ ghadabî = My Mercy has surpassed My Wrath.) [Daylamî]

Its meaning is: “My attribute mercy has surpassed My attribute wrath. That is, it has overwhelmed My wrath towards the sinful ones from among the Believers.” It does not mean that His attribute mercy surpasses the Self’s wrath, which is directed towards disbelievers. (First Volume, 266th Letter)

Hadrat Muhammad Ma’thûm Fârukî states the same thing:
The hostility which Allahu ta’âlâ has against disbelief and disbelievers originates from His Self. He Himself is hostile towards idols such as Lât and Uzzâ and those who worship these idols. Burning eternally in Hell is the retribution for this abominable deed. This is not the case with all other sorts of sins. For the enmity and wrath Allahu ta’âlâ has for these things do not come from Himself. His wrath is one of His Attributes and His torment is one of His Deeds. Therefore, the punishment for these sins is not eternal. (Third Volume, 55th Letter)