Authentic reports declare chess forbidden on the authority of ʿAbd Allah ibn ʿAbbās (1) and ʿAbd Allah ibn ʿUmar (2), and no Companion is known to have opposed them in this matter at all.
Likewise, the three imams and their followers unanimously prohibit it (3). Al-Shāfiʿī never stated that it is lawful, so it is incorrect to claim that the Shāfiʿī school permits it; such an attribution is a falsehood against him. What he actually said was: “As for chess, its prohibition has not become clear to me” (4).
Thus he, may Allah have mercy on him, withheld judgment on declaring it unlawful and did not issue a fatwa allowing it (5).
Those who do forbid it then differed: Is chess more strictly forbidden than nard (the dice game), or is nard more strictly forbidden than chess?
An authentic narration from Ibn ʿUmar states: “Chess is worse than nard” (6).