The completeness of Islaam
The completeness of Islaam obviously means that it cannot be completed further. Believing otherwise would imply one or more of the following dangerous conclusions:
That Allaah was not truthful in declaring this completeness.
That Allaah has forgotten or missed some details needed to complete the Deen.
That Muhammad (peace be upon him) has neglected or forgotten to convey some matters needed to complete the Deen.
This explains why Islaam warns strongly against introducing bid`ahs into the Deen. Imaam Malik said:
“Whoever innovates in Islaam what he believes to be a good bid`ah would be claiming that Muhammad (peace be upon him) has betrayed the trust (of delivering the full Message)…”
He then recited ayah 5:3 from al-Ma`idah.