The single most important message of all prophets to their people was to worship God alone and none else and to follow His teachings. All of them, Noah, Abraham, Isaac, Ishmael, Moses, Aaron, David, Solomon, Jesus, Muhammad and others, in addition to those we do not know - invited people to worship God and shun false gods.
Moses declared: “Hear, O Israel The Lord our God is one Lord.” (Deuteronomy 6:4).
This was repeated 1500 years later by Jesus, when he said: “The first of all the commandments is, ‘Hear, O Israel; the Lord our God is one Lord.’” (Mark 12:29).
Finally, the call of Muhammad some 600 years later reverberated across the hills of Mecca:
“And your God is One God: there is no god but He...” (Quran 2:163)
The Holy Quran states this fact clearly:
“And We did not send any Messenger before you (O Muhammad) but We revealed to him (saying): ‘none has the right to be worshipped but I, so worship Me.’” (Quran 21:25)