Musannaf Ibn Abi Shaybah

Hazrat Abu Raja says that I asked Imam Muhammad about placing dots in the Qur'an? So he replied: I fear that you people will make additions or omissions in the letters. And I asked Hasan? So he replied: Has the statement of Hazrat Umar not reached you, which he wrote in a letter: That you should learn Arabic. And learn to worship in a good manner. And develop understanding in religion.