Sahih Bukhari
Fighting for the Cause of Allah (Jihaad)
Volume: 004 / Book Number: 052 / Hadith Number: 49
Narrated Samura:
The Prophet said, "Last night two men came to me (in a dream) and made me ascend a tree and then admitted me into a better and superior house, better of which I have never seen. One of them said, 'This house is the house of martyrs."