The first Shia Imam, Ali ibn Abitaleb (AS) said:

Allah (SWT) sent the Prophet of Islam (PBUH) when the prophets were not present and nations were in neglectful sleep, and the threads of friendship and humanity were torn. Then the Prophet (PBUH) came among the people while affirming the books of other prophets and with a ‘light’ became a guide for the human being which all the people must obey it and that light is the ‘holy Quran’ [1].

[1] Nahjul Balaghah, Sermon 158.

Source: en.shafaqna.com