Sahih Bukhari
Call to Prayers (Adhaan)
Volume: 001 / Book Number: 011 / Hadith Number: 615
Narrated Anas:
Once the Iqama was pronounced and the Prophet was talking to a man (in a low voice) in a corner of the mosque and he did not lead the prayer till (some of) the people had slept (dozed in a sitting posture) .