Why were so many prophets and books sent?

Dear Brother / Sister,

Depending on the structure of every time and society, various prophets came. The history of humanity has been in a progress. There are steps from the primary school to the university; similarly, the history of humanity experienced such a developmental stage. Decrees and prophets suitable for the conditions of time periods were sent. In the last stage of the humanity, the last prophet came with universal decrees.

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