What are the conditions for the legality of a contest involving projectiles (Nidhal)?

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When a contest involving the throwing of projectiles occurs between two parties, it is stipulated that the projectiles must be divisible among them without breaking, and that the shares must be equal. If there are three parties, each must be entitled to a third, and if there are four parties, each must be entitled to a quarter, and so on for any larger number. This is mandatory because if the projectiles are not divisible according to the number of participants, one or more shares will remain that the group cannot jointly participate in.