If a Muslim is one who believes in Prophet Muhammad (pbuh) and Allaah – How can Moses or Jesus be Muslims?
If a Muslim is one who believe in Prophet Muhammad ﷺ and Allaah, how can Moses or Jesus be Muslims if Muhammad ﷺ was not born or did not live at their times?
To answer this, a person must first understand the concept of an Ummah or nation in Islam. An Ummah is defined as a group of people, a tribe or a nation. Until the advent of Muhammad ﷺ, Messengers were sent by God to specific groups of people, the Qur’aan teaches us:
For every people (Ummah – أُمَّةٍ) there is a messenger; and when their messenger is come the matter is decided between them equitably, and no one is wronged. – Qur’aan 10:47.
A messenger or Rasūl ( رَّسُولٌ) is sent with a message or Risālah (رسالة). A Muslim is one who believes in the message, the messenger and the one who sent the message – God. In the Qur’aan, God relates that He sent messengers to many people and those who rejected the message, the messengers and therefore God, are considered disbelievers:
Remember We gave Moses the Book and sent after him many an apostle; and to Jesus, son of Mary, We gave clear evidence of the truth, reinforcing him with divine grace. Even so, when a messenger brought to you what did not suit your mood you turned haughty, and called some imposters and some others you slew. And they say: “Our hearts are enfolded in covers.” In fact God has cursed them for their unbelief; and only a little do they believe. – Qur’aan 2:87-88.
Both Moses and Jesus believed in God and the message God gave them, therefore they would be considered Muslims. The people to whom they preached to and who believed in Moses and Jesus, along with the messages from God given to them, would also be considered Muslims. Today, the current Ummah or nation, is not one tribe or nation, Muhammad ﷺ was sent as a messenger with a message for the entire world:
And We have not sent you, [O Muhammad], except as a mercy to the worlds. – Qur’aan 21:107.
Therefore Muslims today are those who accept the messenger (Muhammad ﷺ) and his message, the Qur’aan.
and God knows best.