Search for "muck" to find the relevant entry, also below for convenience:
Any player who has been a legal part of the game can ask to see a called hand, even if the cards have already been mucked. Abuse of this privilege can result in denial by the dealer. When a winning player asks to see a mucked hand, that hand will be considered live, and the winning player can lose their pot. When any other players ask to see a folded hand, the hand will remain dead.
See here for the Texas Holdem rules that WSOP uses: https://www.wsop.com/poker-games/texas-holdem/rules/
Search for "muck" to find the relevant entry, also below for convenience:
Any player who has been a legal part of the game can ask to see a called hand, even if the cards have already been mucked. Abuse of this privilege can result in denial by the dealer. When a winning player asks to see a mucked hand, that hand will be considered live, and the winning player can lose their pot. When any other players ask to see a folded hand, the hand will remain dead.