Imām Ibn al-Qayyim (d. 721 AH) said:

“If it is said: ‘we should [think only good thoughts of Allāh], for such is the subsequent nature of His magnanimous forgiveness, mercy, pardon, and goodness. Truly, His mercy precedes His anger. He does not derive benefit from punishing [his slaves] and forgiving them does not harm Him in the least.’

We say [in response]: This matter is [as described]. Nay, Allāh is above even this narrative. For He is more exalted, generous, full of goodness, and more merciful [than that]. However, these [attributes] must be applied to the correct context. For He, the Exalted, is also described with the attributes of wisdom, power, retribution, vengeful seizure, and punishment of those deserving of punishment. So, if positive thinking [concerning Allāh] applied solely to His names and attributes [of mercy], both the pious and the criminal, the muʾmin and the disbeliever, and the close ally [of Allāh] and His enemy would all be equal [in their belief]. Nay, [Allāh’s] names and attributes [of mercy] hold no benefit for the ones who choose criminality and to return with His wrath, anger, and voluntarily make themselves amenable to His curse. [How could this be] when they rush towards that which is forbidden, carelessly stripping it of any inviolability? Rather, [let him know] that positive thinking [of Allāh] only holds benefit for the one who turns to Him in repentance, regret, refrains from that which he was engaging in, and exchanges his misdeeds for actions of righteousness. He meets his remaining years with goodness and obedience. Then, [and only then], does he think positively [of Allāh]. This is true ḥusn al-ẓann [positive thinking], whereas what comes before it is unadulterated deception! And Allāh alone is the one sought for all relief.”

Source: Al-Dāʾ wa-al-Dawāʾ’:49
Translated by: Riyāḍ al-Kanad