Sahih Bukhari Volume 008, Book 076, Hadith Number 424.

Narated By Sahl : I heard the Prophet saying, "A (small) place equal to an area occupied by a whip in Paradise is better than the (whole) world and whatever is in it; and an undertaking (journey) in the forenoon or in the afternoon for Allah's Cause, is better than the whole world and whatever is in it."