I used to recognize the completion of the prayer of the Prophet (ﷺ) by hearing Takbir.
Sahih al-Bukhari Book 10, Hadith 234
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(the freed slave of Ibn `Abbas) Ibn `Abbas told me, "In the lifetime of the Prophet (ﷺ) it was the custom to celebrate Allah's praises aloud after the compulsory congregational prayers." Ibn `Abbas further said, "When I heard the Dhikr, I would learn that the compulsory congregational prayer had ended."
Sahih al-Bukhari Book 10, Hadith 233 Next Hadith → Some poor people came to the Prophet (ﷺ) and said, "The wealthy people will get higher grades and will have permanent enjoyment and they pray like us and fast as we do. They have more money by which they perform the Hajj, and `Umra; fight and struggle in Allah's Cause and give in charity." The Prophet said, "Shall I not tell you a thing upon which if you acted you would catch up with those who have surpassed you? Nobody would overtake you and you would be better than the people amongst whom you live except those who would do the same. Say "Subhana l-lah", "Al hamdu li l-lah" and "Allahu Akbar" thirty three times each after every (compulsory) prayer." We differed and some of us said that we should say, "Subhan-al-lah" thirty three times and "Al hamdu li l-lah" thirty three times and "Allahu Akbar" thirty four times. I went to the Prophet (ﷺ) who said, "Say, "Subhan-al-lah" and "Al hamdu li l-lah" and "Allahu Akbar" all together , thirty three times."
Sahih al-Bukhari Book 10, Hadith 235
Sahih al-Bukhari Book 10, Hadith 233 Next Hadith → Some poor people came to the Prophet (ﷺ) and said, "The wealthy people will get higher grades and will have permanent enjoyment and they pray like us and fast as we do. They have more money by which they perform the Hajj, and `Umra; fight and struggle in Allah's Cause and give in charity." The Prophet said, "Shall I not tell you a thing upon which if you acted you would catch up with those who have surpassed you? Nobody would overtake you and you would be better than the people amongst whom you live except those who would do the same. Say "Subhana l-lah", "Al hamdu li l-lah" and "Allahu Akbar" thirty three times each after every (compulsory) prayer." We differed and some of us said that we should say, "Subhan-al-lah" thirty three times and "Al hamdu li l-lah" thirty three times and "Allahu Akbar" thirty four times. I went to the Prophet (ﷺ) who said, "Say, "Subhan-al-lah" and "Al hamdu li l-lah" and "Allahu Akbar" all together , thirty three times."
Sahih al-Bukhari Book 10, Hadith 235