Is it true that Allah legislated that Messengers are not killed by their peoples, whereas Prophets who are not Messengers can be killed, as is evident from the attempts of the Children of Israel to kill Jesus and Muhammad and their failure to do so, while they killed many Prophets?

There is no explicit evidence preventing the killing of messengers. Rather, the apparent meaning of the Quranic texts indicates the possibility and occurrence of such an act, as in His (Allah's) saying: "Say, 'Already did messengers come to you before me with clear proofs and with what you said. So why did you kill them, if you should be truthful?'" and "Is it that whenever a messenger came to you with that which your souls did not desire, you were arrogant? And a party [of messengers] you denied and another party you killed?" This confirms that some messengers were indeed killed. The Quran also referred to the possibility of the killing of the Messenger Muhammad (peace be upon him) with His saying: "So if he was to die or be killed, would you turn back on your heels?" This is coupled with the reminder that Allah protected him from people thereafter, and that some Companions, like Ibn Mas'ud (may Allah be pleased with him), affirmed that the Prophet (peace be upon him) died a martyr, affected by the poison he had consumed. The statement that messengers are not killed is contradicted by these proofs, although some scholars have differentiated between being killed in jihad and otherwise, emphasizing that those messengers who were killed were not killed in jihad.