Sahih Bukhari Volume 4, Book 52, Hadith Number 141.

Narated By Abu Huraira : The Prophet said, “Charity is obligatory everyday on every joint of a human being. If one helps a person in matters concerning his riding animal by helping him to ride it or by lifting his luggage on to it, all this will be regarded charity. A good word, and every step one takes to offer the compulsory Congregational prayer, is regarded as charity; and guiding somebody on the road is regarded as charity.”