It is narrated from Ibn Abbas (may Allah be pleased with him), he states: "I used to recognize the conclusion of the prayer of the Messenger of Allah (peace be upon him) by the sound of the takbeer (Allahu Akbar)." Amr bin Dinar (may Allah have mercy on him) says: "Later, I mentioned this hadith to Abu Ma'bad, and he said: I did not narrate this hadith to you," Amr says: "Even though he was the one who narrated it to me," and he said: "He is the most truthful among the freed slaves of Ibn Abbas (may Allah be pleased with him)." Imam Shafi'i (may Allah have mercy on him) says: "It is as if he forgot after narrating this hadith to them."
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 266
Hadith Takhrijأخرجہ البخاری، الأذان، باب الذکر بعد الصلاۃ: 842 - ومسلم، المساجد، باب الذکر بعد الصلاۃ: 583۔