كتاب الجهاد والسير
Fighting for the Cause of Allah (Jihaad)
Chapter: Supporting with reinforcements
باب الْعَوْنِ بِالْمَدَدِ
Sahih al-Bukhari 3064

Narrated Anas:

The people of the tribes of Ril, Dhakwan, 'Usiya and Bani Lihyan came to the Prophet (ﷺ) and claimed that they had embraced Islam, and they requested him to support them with some men to fight their own people. The Prophet (ﷺ) supported them with seventy men from the Ansar whom we used to call Al-Qurra'(i.e. Scholars) who (out of piety) used to cut wood during the day and pray all the night. So, those people took the (seventy) men till they reached a place called Bi'r-Ma'ana where they betrayed and martyred them. So, the Prophet (ﷺ) invoked evil on the tribe of Ril, Dhakwan and Bani Lihyan for one month in the prayer.

Narrated Qatada: Anas told us that they (i.e. Muslims) used to recite a Quranic Verse concerning those martyrs which was:-- "O Allah! Let our people be informed on our behalf that we have met our Lord Who has got pleased with us and made us pleased." Then the Verse was cancelled.

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ، وَسَهْلُ بْنُ يُوسُفَ، عَنْ سَعِيدٍ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ ـ رضى الله عنه أَنَّ النَّبِيَّ صلى الله عليه وسلم أَتَاهُ رِعْلٌ وَذَكْوَانُ وَعُصَيَّةُ وَبَنُو لِحْيَانَ، فَزَعَمُوا أَنَّهُمْ قَدْ أَسْلَمُوا، وَاسْتَمَدُّوهُ عَلَى قَوْمِهِمْ، فَأَمَدَّهُمُ النَّبِيُّ صلى الله عليه وسلم بِسَبْعِينَ مِنَ الأَنْصَارِ قَالَ أَنَسٌ كُنَّا نُسَمِّيهِمُ الْقُرَّاءَ، يَحْطِبُونَ بِالنَّهَارِ وَيُصَلُّونَ بِاللَّيْلِ، فَانْطَلَقُوا بِهِمْ حَتَّى بَلَغُوا بِئْرَ مَعُونَةَ غَدَرُوا بِهِمْ وَقَتَلُوهُمْ، فَقَنَتَ شَهْرًا يَدْعُو عَلَى رِعْلٍ وَذَكْوَانَ وَبَنِي لِحْيَانَ‏.‏ قَالَ قَتَادَةُ وَحَدَّثَنَا أَنَسٌ أَنَّهُمْ قَرَءُوا بِهِمْ قُرْآنًا أَلاَ بَلِّغُوا عَنَّا قَوْمَنَا بِأَنَّا قَدْ لَقِينَا رَبَّنَا فَرَضِيَ عَنَّا وَأَرْضَانَا‏.‏ ثُمَّ رُفِعَ ذَلِكَ بَعْدُ‏.‏
Reference : Sahih al-Bukhari 3064
In-book reference : Book 56, Hadith 269
USC-MSA web (English) reference : Vol. 4, Book 52, Hadith 299
  (deprecated numbering scheme)