Mukhtasar Bukhari

Narrated Ibn Abbas (may Allah be pleased with them) that when the people finished the obligatory prayer, raising the voice in remembrance (of Allah) was (practiced) in the era of the Prophet (peace and blessings of Allah be upon him), and Ibn Abbas (may Allah be pleased with them) also said that when I used to hear the people returning while remembering (Allah), I would know that the prayer had been completed.