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Now that you are familiar with the various opinions on this question, let us set out (1) the proofs offered by both sides and the textual grounds each camp relies upon. We place the matter before the fair-minded; as for anyone else, neither Allah, His Messenger, nor the people of knowledge accord him any weight at all.

Those who allow a wager without the presence of a muhallil argue:
• Allah, Exalted be He, says: “O you who believe, fulfill all contracts” (al-Mā’idah 5:1). This verse commands fulfillment of every agreement—except an agreement that Allah and His Messenger have forbidden or one upon whose prohibition the entire ummah has reached consensus (2). Since a bilateral wager is subject to none of these exceptions, the two contracting parties are obliged to honor it.
• Allah, Exalted be He, also says: “And fulfill the covenant, for every covenant will be questioned about” (al-Isrā’ 17:34).
• And He says: “And those who keep their covenants whenever they make one” (al-Baqarah 2:177).
• The Prophet ﷺ said: “Muslims are bound by their conditions, except a condition that makes the unlawful lawful or the lawful unlawful.” (3) This is an authentic hadith.