What is the ruling on Istijmar and its evidence from the Qur’an and Sunnah, and is prayer valid with Tayammum due to the harm caused by using cold water for Istinja’?

Istijmar is the use of stones or similar materials to remove what exits from the two private parts. It is permissible by scholarly consensus, and it is permissible even if water is available, provided that the impurity does not exceed its usual place of exit. It is not sufficient to use fewer than three stones or wipes. If purity is achieved with less than three, it is obligatory to complete the number to three. If purity is not achieved with three, it is obligatory to continue wiping until the area is clean. It is recommended to use an odd number of wipes. A small trace that cannot be removed except by water is excused. It is important to note that Tayammum (definition) (dry ablution) is not permissible when one is able to use water, even if it requires heating it. Prayers performed with Tayammum while water was available must be repeated, unless the use of water would be harmful, in which case Tayammum is permissible. The majority of scholars do not permit combining prayers for illness.