Is it permissible to kill the horse with a gasoline injection to relieve it from the pain of its broken leg that cannot be treated?

It is permissible to eat horse meat according to the most preponderant opinion of the scholars ( according to the prevailing opinion among the Shafi'i and Hanbali scholars), and its evidence is what is mentioned in the two Sahihs (authentic collections of Hadith) from Asma bint Abi Bakr and Jabir bin Abdullah that the Companions slaughtered a horse during the time of the Prophet, peace and blessings be upon him, and they ate it, and that he, peace and blessings be upon him, permitted horse meat. However, it is not permissible to kill them in the manner mentioned in the question because that involves wasting wealth, which is prohibited. Rather, it should be slaughtered and eaten, or its meat should be distributed to the needy.