كتاب الإيمان
1
The Book of Faith
(17)
Chapter: The evidence that one of the attributes of faith is to love for one's brother muslim that one loves for oneself of goodness
(17)
باب الدَّلِيلِ عَلَى أَنَّ مِنْ خِصَالِ الإِيمَانِ أَنْ يُحِبَّ لأَخِيهِ الْمُسْلِمِ مَا يُحِبُّ لِنَفْسِه مِنَ الْخَيْرِ

It is narrated on the authority of Anas b. Malik that the Prophet (may peace and blessings be upon him) observed:

"None amongst you believes (truly) until he loves for his brother" - or he said "for his neighbour" - "that which he loves for himself."
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَابْنُ، بَشَّارٍ قَالاَ حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، قَالَ سَمِعْتُ قَتَادَةَ، يُحَدِّثُ عَنْ أَنَسِ بْنِ مَالِكٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ لاَ يُؤْمِنُ أَحَدُكُمْ حَتَّى يُحِبَّ لأَخِيهِ - أَوْ قَالَ لِجَارِهِ - مَا يُحِبُّ لِنَفْسِهِ ‏"‏ ‏.‏
Reference : Sahih Muslim 45 a
In-book reference : Book 1, Hadith 77
USC-MSA web (English) reference : Book 1, Hadith 72
  (deprecated numbering scheme)