Is it permissible to follow a ma'mum (one praying behind the imam)?

The questioner : Is it permissible to follow a ma'mum (one praying behind the imam)?

The Shaykh : No, it is not permissible; because it did not occur in the time of the Messenger (peace be upon him), nor in any era of the righteous Salaf. It is mentioned in "Sahih al-Bukhari" in the story of the Prophet (peace and blessings be upon him) going out one morning to relieve himself, and al-Mughirah ibn Shu'bah was with him. When the time for wudu' (the ablution for prayer) came, al-Mughirah poured water for the Prophet's (peace and blessings be upon him) wudu'. The people were waiting for him (peace be upon him) to lead them in prayer as was his custom. When they delayed him, they brought forward 'Abd al-Rahman ibn 'Awf, and he led them in prayer. Then al-Mughirah came with the Prophet (peace and blessings be upon him and his family). Al-Mughirah intended to inform the imam of the arrival of the Messenger (peace and blessings be upon him) so that he would step back, but the Prophet (peace and blessings be upon him) gestured to him to let him continue. So the Prophet (peace and blessings be upon him) and al-Mughirah followed 'Abd al-Rahman ibn 'Awf. Then 'Abd al-Rahman said the taslim (the closing salam of prayer), and they stood up and completed the rak'ah (a unit of prayer) that they had missed. Al-Mughirah did not follow the Messenger (peace be upon him) in completing this prayer as some do today. Likewise, the scenarios you mentioned earlier, where a man comes in after the imam has said the taslim, finds some of the masbuq (one who joins the prayer late), and follows him, this scenario never occurred.
And the second congregation, in any case, is not prescribed in the mosque; because all of the righteous Salaf, when they missed the prayer with the congregation, prayed individually. And Imam al-Shafi'i (may Allah have mercy on him) said in his book "Al-Umm": "We have preserved that a group of the Companions of the Prophet (peace and blessings be upon him and his family) missed the prayer with the congregation, so they prayed individually, although they were able to gather again, but they did not do so; because they disliked to gather in a mosque twice."