Sahih Muslim 45
Sahih Muslim · Book 1: The Book of Faith · The evidence that one of the attributes of faith is to love for one's brother muslim that one loves for oneself of goodness
It is narrated on the authority of Anas that the Prophet (may peace blessings be upon him) observed:
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 " .
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.