Repeating Fajr with the congregation for one who has already prayed on his own

Jabir bin Yazid bin Al-Aswad Al Amir told us that his father said:

"I attended Fajr prayer with the Messenger of Allah ﷺin Masjid Al Khaif. When he finished praying, he saw two men at the back of the people who had not prayed with him. He said: 'Bring them here.' So they were brought to him, trembling. He said: 'What kept you from praying with us? They said: '0 Messenger of Allah ﷺ we has already prayed in our lodgings.' He said: 'Do not do that. If you have already prayed in your lodgings, then you come to a Masjid in which there is a
congregation, then pray with them, and it will be a voluntary prayer for you."'

أَخْبَرَنَا زِيَادُ بْنُ أَيُّوبَ، قَالَ حَدَّثَنَا هُشَيْمٌ، قَالَ حَدَّثَنَا يَعْلَى بْنُ عَطَاءٍ، قَالَ حَدَّثَنَا جَابِرُ بْنُ يَزِيدَ بْنِ الأَسْوَدِ الْعَامِرِيُّ، عَنْ أَبِيهِ، قَالَ شَهِدْتُ مَعَ رَسُولِ اللَّهِ ﷺ صَلاَةَ الْفَجْرِ فِي مَسْجِدِ الْخَيْفِ فَلَمَّا قَضَى صَلاَتَهُ إِذَا هُوَ بِرَجُلَيْنِ فِي آخِرِ الْقَوْمِ لَمْ يُصَلِّيَا مَعَهُ قَالَ " عَلَىَّ بِهِمَا " . فَأُتِيَ بِهِمَا تُرْعَدُ فَرَائِصُهُمَا فَقَالَ " مَا مَنَعَكُمَا أَنْ تُصَلِّيَا مَعَنَا " . قَالاَ يَا رَسُولَ اللَّهِ إِنَّا قَدْ صَلَّيْنَا فِي رِحَالِنَا . قَالَ " فَلاَ تَفْعَلاَ إِذَا صَلَّيْتُمَا فِي رِحَالِكُمَا ثُمَّ أَتَيْتُمَا مَسْجِدَ جَمَاعَةٍ فَصَلِّيَا مَعَهُمْ فَإِنَّهَا لَكُمَا نَافِلَةٌ " .