Maliks Muwatta Book 003, Hadith Number 001.

Section : The Call to Prayer.

Yahya related to me from Malik that Yahya ibn Said said, "The Messenger of Allah, may Allah bless him and grant him peace, had wanted to take two pieces of wood to strike them together to gather people for the prayer, and Abdullah ibn Zayd al-Ansari, then of the tribe of Harith ibn al-Khazraj, was shown two pieces of wood in his sleep. He said, 'These are close to what the Messenger of Allah, may Allah bless him and grant him peace, wants.' Then it was said, 'Do you not call to the prayer?', so when he woke up he went to the Messenger of Allah, may Allah bless him and grant him peace, and mentioned the dream to him. The Messenger of Allah, may Allah bless him and grant him peace, ordered the adhan."