Is despairing of God's mercy considered an act of disbelief that expels one from the faith, and are the rulings concerning disbelievers applied to them, as stated in the noble verse: "O my sons, go and find out about Joseph and his brother and do not despair of the relief of Allah. Indeed, no one despairs of the relief of Allah except the disbelieving people"?

Despairing of the spirit of Allah is one of the gravest major sins, and Ibn Mas'ud (may Allah be pleased with him) considered it as such. Scholars have adduced evidence for it being a major sin from Allah's saying: ﴿Indeed, no one despairs of the Spirit of Allah except the disbelieving people.﴾ and His saying: ﴿And who despairs of the mercy of his Lord except those astray?﴾, and because it necessitates belying definitive texts. Some have considered it a type of disbelief if its cause is the denial of the vastness of Allah's mercy. However, if it is due to magnifying one's sins, then it is a major sin and not disbelief. Based on this, despairing of Allah's mercy is a major sin, a characteristic of disbelievers, and a transgression that may lead to disbelief if it reaches the point of denying the vastness of Allah's mercy.