What is the ruling on those who buy goods from a merchant who deliberately withholds them to restrict their availability, despite having no need for them, thereby encouraging traders to exercise monopoly?

Whoever purchases commodities from a monopolist without having a need for them, when other means of obtaining them or alternative goods are available, assists the merchant in disobeying Allah Almighty and thereby commits a forbidden act and a sin. However, a person who has a genuine need for such goods and no alternative means of obtaining them is excused by necessity, and the sin falls solely upon the seller.

Monopoly (ihtikar) is strictly prohibited in Islam. The Prophet (peace and blessings be upon him) said, “None monopolizes except the sinner”
(recorded by Imam Ahmad in his Musnad, Muslim in his Ṣahiḥ, Abu Dawud, at-Tirmidhi (who declared it authentic), Ibn Majah in his Sunan, al-Darimi in his Sunan, and al-Bayhaqi in Al-Sunan al-Kubra and Shuʿab al-Iman). Whoever knowingly buys such goods from a merchant who exploits people’s needs, when not compelled by necessity or when other means or alternative goods are available, incurs the same sin as the merchant. Allah Almighty says, “And cooperate in righteousness and piety, but do not cooperate in sin and aggression” (Quran, 5:2). This verse clearly demonstrates the prohibition of assisting in sin, and that committing the sin directly is even more so.

In contrast, no sin is incurred by a person who is compelled by necessity to purchase such goods at inflated prices when no other means of obtaining them exist; the blame lies entirely with the seller. The Exalted is He says, “…except what you are compelled to [consume]” (Quran, 6:119). Additionally, the legal maxim states that a need may be treated as a necessity under Islamic law, meaning that when a situation calls for ease or facilitation to achieve legitimate purpose, it is granted a similar concession to that of a necessity. Though a concession granted to meet a need may continue to be applicable as long as the need persists, a concession based on a necessity is limited to the period during which that necessity exists.

And Allah Almighty knows best.