It is narrated from Sayyiduna Bilal (may Allah be pleased with him) that he said to the Prophet (peace and blessings be upon him): "Do not say Amin before me."
(b) Waki' narrated it from Sufyan with these words: "From Bilal, that he said: 'O Messenger of Allah!'" The narration of Abd al-Razzaq is more correct.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2439