How can one reconcile God's prohibition of casting oneself into perdition with the prophets being given a choice between life and death, as happened with the Prophet Muhammad, peace and blessings be upon him, knowing that there is no contradiction in Islamic law?

There is no contradiction in choosing death if it does not involve harm or casting oneself into destruction. Rather, it is a choice for what is better, for meeting Allah, and for enjoying the bliss of Paradise. It has been reported that the Prophet, peace and blessings be upon him, was given a choice between this world and what is with Allah, and he chose what is with Allah. Prophets are given a choice before their souls are taken, between this world and the Highest Companion. A believer loves to meet Allah when given glad tidings of His mercy and Paradise, whereas a disbeliever dislikes meeting Allah when given tidings of His torment and wrath.