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 that the Prophet (may peace blessings be upon him) observed:

By Him in whose Hand is my life, no, bondsman (truly) believes till he likes for his neighbour, or he (the Holy Prophet) said: for his brother, whatever he likes for himself.
وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، عَنْ حُسَيْنٍ الْمُعَلِّمِ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ وَالَّذِي نَفْسِي بِيَدِهِ لاَ يُؤْمِنُ عَبْدٌ حَتَّى يُحِبَّ لِجَارِهِ - أَوْ قَالَ لأَخِيهِ - مَا يُحِبُّ لِنَفْسِهِ ‏"‏ ‏.‏
Reference : Sahih Muslim 45 b
In-book reference : Book 1, Hadith 78
USC-MSA web (English) reference : Book 1, Hadith 73
  (deprecated numbering scheme)