It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the iqamah for the prayer was called while the Prophet (peace and blessings be upon him) was talking with a man in a corner of the mosque. He (peace and blessings be upon him) did not begin the prayer until the people began to doze.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2296