[Machine] He was with the Prophet ﷺ during the Farewell Pilgrimage. He prayed the Fajr prayer in the Mosque of al-Khaif. When he had finished his prayer, he saw two men at the back of the mosque. They were brought to him by thunder. He said, "Why did you not pray with us?" One of them said, "O Messenger of Allah, we prayed while traveling, then we came while you were praying, so we sat down." The Messenger of Allah ﷺ said, "When one of you prays in his riding mount and then comes while the Imam is praying, let him pray with him, for it will be a voluntary prayer for him.
أَنَّهُ كَانَ مَعَ النَّبِيِّ ﷺ فِي حَجَّةِ الْوَدَاعِ فَصَلَّى الْفَجْرَ فِي مَسْجِدِ الْخَيْفِ فَلَمَّا قَضَى صَلَاتَهُ إِذَا رَجُلَانِ فِي مُؤَخَّرِ الْمَسْجِدِ فَأُتِيَ بِهِمَا تَرْعَدُ فَرَائِصُهُمَا قَالَ مَا لَكُمَا لَمْ تُصَلِّيَا مَعَنَا فَقَالَ يَا رَسُولَ اللهِ صَلَّيْنَا فِي رِحَالِنَا ثُمَّ جِئْنَا وَأَنْتَ تُصَلِّي فَجَلَسْنَا فَقَالَ رَسُولُ اللهِ ﷺ إِذَا صَلَّى أَحَدُكُم فِي رَحْلِهِ ثُمَّ جَاءَ وَالْإِمَامُ يُصَلِّي فَلْيُصَلِّ مَعَهُ فَإِنَّهَا لَه نَافِلَةٌ