And the infidels said why the Quran was not sent down on them all at once? We have thus sent it down gradually that We may strengthen your heart there with and We recited it with gradual recitation.[25:32]
It is narrated on the authority of 'Uthman that the Messenger of Allah (may peace be upon him) said. He who died knowing (fully well) that there is no god but Allah entered Paradise.