Narrated Abu Ma`bad
(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."
Narrated Ibn `Abbas
I used to recognize the completion of the prayer of the Prophet (ﷺ) by hearing Takbir.
Narrated Abu Huraira
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."
Narrated Warrad
(the clerk of Al-Mughira bin Shu`ba) Once Al-Mughira dictated to me in a letter addressed to Muawiya that the Prophet (ﷺ) used to say after every compulsory prayer, "La ilaha illa l-lahu wahdahu la sharika lahu, lahu l-mulku wa lahu l-hamdu, wa huwa `ala kulli shay'in qadir. Allahumma la mani`a lima a`taita, wa la mu`tiya lima mana`ta, wa la yanfa`u dhal-jaddi minka l-jadd. [There is no Deity but Allah, Alone, no Partner to Him. His is the Kingdom and all praise, and Omnipotent is he. O Allah! Nobody can hold back what you gave, nobody can give what You held back, and no struggler's effort can benefit against You]." And Al-Hasan said, "Al-jadd' means prosperity [??]."