The Sahabah (may Allah be pleased with them) were very keen to follow in the footsteps of the Prophet (blessings and peace of Allah be upon him) in all things, and to transmit that to those who came after them. Part of the practice of the Prophet (blessings and peace of Allah be upon him) and his companions was to remember Allah (dhikr) after the prescribed prayers, and to raise their voices in doing that. In this hadith, Abu Ma‘bad, the freed slave of ‘Abdullah ibn ‘Abbas, narrates that Ibn ‘Abbas(may Allah be pleased with him) told him that raising the voice in dhikr is something that was narrated from the Prophet (blessings and peace of Allah be upon him), meaning the dhikrs and du‘a’s that followed the prayer, such as seeking forgiveness (istighfar), glorifying Allah (tasbih), praising Him (tahmid) and magnifying Him (takbir), when the people had finished the obligatory prayer. This is something that happened and was practised at the time of the Messenger (blessings and peace of Allah be upon him). What is meant by finishing the prayer is the taslim. Ibn ‘Abbas (may Allah be pleased with him) would know that the people had finished the prayer when he heard the dhikr. This highlights the fact that it is permissible to say dhikr out loud following the prayer. This hadith may be understood as meaning that the Prophet (blessings and peace of Allah be upon him) only said it out loud in order to teach the people what to say in dhikr, not that he always did that..