Sunan an-Nasa'i 3607
It was narrated that Al-Ahnaf bin Qais said:
"We set out for Hajj, and came to Al-Madinah intending to perform Hajj. While we were in our camping place unloading our mounts, someone came to us and said: 'The people have gathered in the Masjid and there is panic.' So we set out and found the people gathered around a group in the middle of the Masjid, among whom were 'Ali, Az-Zubair, Talhah and Sa'd bin Abi Waqqas. While we were like that, 'Uthman came, wearing a yellowish cloak with which he had covered his head. He said: Is 'Ali here? Is Talhah here? Is Az-Zubair here? Is Sa'd here? They said: Yes. He said: I adjure you by Allah, beside Whom there is none worthy of worship, are you aware that the Messenger of Allah said: Whoever buys the Mirbad of Banu so and so, Allah will forgive him, and I bought it for twenty or twenty-five thousand, then I came to the Messenger of Allah and told him, and he said: Add it to our Masjid and the reward for it will be yours? They said: By Allah, yes. He said: 'I adjure you by Allah, beside Whom there is none worthy of worship, are you aware that the Messenger of Allah said: Whoever buys the well of Rumah, Allah will forgive him, so I bought it for such and such an amount, then I came to the Messenger of Allah and told him, and he said: Give it to provide water for the Muslims, and the reward for it will be yours?' They said: By Allah, yes. He said: 'I adjure you by Allah, beside Whom there is none worthy of worship, are you aware that the Messenger of Allah said: Whoever equips these (men), Allah will forgive him, -meaning the army of Al-'Usrah (i.e. Tabuk)- so I equipped them until they were not lacking even a rope or a bridle?' They said: By Allah, yes. He said: O Allah, bear witness, O Allah, bear witness."
أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ بْنُ إِدْرِيسَ، قَالَ سَمِعْتُ حُصَيْنَ بْنَ عَبْدِ الرَّحْمَنِ، يُحَدِّثُ عَنْ عَمْرِو بْنِ جَاوَانَ، عَنِ الأَحْنَفِ بْنِ قَيْسٍ، قَالَ خَرَجْنَا حُجَّاجًا فَقَدِمْنَا الْمَدِينَةَ وَنَحْنُ نُرِيدُ الْحَجَّ فَبَيْنَا نَحْنُ فِي مَنَازِلِنَا نَضَعُ رِحَالَنَا إِذْ أَتَانَا آتٍ فَقَالَ إِنَّ النَّاسَ قَدِ اجْتَمَعُوا فِي الْمَسْجِدِ وَفَزِعُوا ‏.‏ فَانْطَلَقْنَا فَإِذَا النَّاسُ مُجْتَمِعُونَ عَلَى نَفَرٍ فِي وَسَطِ الْمَسْجِدِ وَإِذَا عَلِيٌّ وَالزُّبَيْرُ وَطَلْحَةُ وَسَعْدُ بْنُ أَبِي وَقَّاصٍ فَإِنَّا لَكَذَلِكَ إِذْ جَاءَ عُثْمَانُ بْنُ عَفَّانَ عَلَيْهِ مُلاَءَةٌ صَفْرَاءُ قَدْ قَنَّعَ بِهَا رَأْسَهُ فَقَالَ أَهَا هُنَا عَلِيٌّ أَهَا هُنَا طَلْحَةُ أَهَا هُنَا الزُّبَيْرُ أَهَا هُنَا سَعْدٌ قَالُوا نَعَمْ ‏.‏ قَالَ فَإِنِّي أَنْشُدُكُمْ بِاللَّهِ الَّذِي لاَ إِلَهَ إِلاَّ هُوَ أَتَعْلَمُونَ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ مَنْ يَبْتَاعُ مِرْبَدَ بَنِي فُلاَنٍ غَفَرَ اللَّهُ لَهُ ‏"‏ ‏.‏ فَابْتَعْتُهُ بِعِشْرِينَ أَلْفًا أَوْ بِخَمْسَةٍ وَعِشْرِينَ أَلْفًا فَأَتَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم فَأَخْبَرْتُهُ فَقَالَ ‏"‏ اجْعَلْهَا فِي مَسْجِدِنَا وَأَجْرُهُ لَكَ ‏"‏ ‏.‏ قَالُوا اللَّهُمَّ نَعَمْ ‏.‏ قَالَ فَأَنْشُدُكُمْ بِاللَّهِ الَّذِي لاَ إِلَهَ إِلاَّ هُوَ أَتَعْلَمُونَ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ مَنْ يَبْتَاعُ بِئْرَ رُومَةَ غَفَرَ اللَّهُ لَهُ ‏"‏ ‏.‏ فَابْتَعْتُهُ بِكَذَا وَكَذَا فَأَتَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم فَقُلْتُ قَدِ ابْتَعْتُهَا بِكَذَا وَكَذَا ‏.‏ قَالَ ‏"‏ اجْعَلْهَا سِقَايَةً لِلْمُسْلِمِينَ وَأَجْرُهَا لَكَ ‏"‏ ‏.‏ قَالُوا اللَّهُمَّ نَعَمْ ‏.‏ قَالَ فَأَنْشُدُكُمْ بِاللَّهِ الَّذِي لاَ إِلَهَ إِلاَّ هُوَ أَتَعْلَمُونَ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَظَرَ فِي وُجُوهِ الْقَوْمِ فَقَالَ ‏"‏ مَنْ جَهَّزَ هَؤُلاَءِ اللَّهُ غَفَرَ لَهُ ‏"‏ ‏.‏ يَعْنِي جَيْشَ الْعُسْرَةِ فَجَهَّزْتُهُمْ حَتَّى مَا يَفْقِدُونَ عِقَالاً وَلاَ خِطَامًا ‏.‏ قَالُوا اللَّهُمَّ نَعَمْ ‏.‏ قَالَ اللَّهُمَّ اشْهَدِ اللَّهُمَّ اشْهَدْ ‏.‏