What is the interpretation of the Almighty’s saying, "And Muhammad is not but a messenger. [Other] messengers have certainly passed on before him. So if he was to die or be killed, would you turn back on your heels [in disbelief]?" (Quran 3:144)? And did anyone apostatize after the death of the Prophet, peace and blessings be upon him, and who were they? And does the hadith "You do not know what they did after you" apply to those born after the era of the Prophet?

The interpretation of the noble verse (And Muhammad is not but a Messenger; [other] messengers have passed on before him. So if he was to die or be killed, would you turn back on your heels? And he who turns back on his heels will never harm Allah at all; but Allah will reward the grateful) Al-Imran/144:

- These verses were revealed after the Battle of Uhud to prepare the Muslims for the death of the Prophet, peace and blessings be upon him, reminding them that Islam does not end with the death or killing of its prophet, and that previous prophets died and this did not affect their followers.

- Allah rebuked those who turned back on their heels and praised the grateful who remained steadfast in their religion.

- The verse indicates the purification of Abu Bakr Al-Siddiq and the noble Companions, as Allah described those who remain steadfast in calamity as "the grateful."

- Abu Bakr Al-Siddiq used this verse, along with the Almighty's saying (Indeed, you are to die, and indeed, they are to die), upon the death of the Prophet, peace and blessings be upon him. He was among those who fought the apostates, which indicates his steadfastness and greatness.

- This verse guides the believers to remain steadfast in faith and not to waver with the loss of leaders, and that their goal is to establish Allah's religion and strive for it.

- Allah protected the Muhajirun and Ansar from apostasy, and Abu Bakr strengthened them with clear verses.