Sahih Bukhari Volume 003, Book 031, Hadith Number 126.

Narated By Ibn 'Abbas : The Prophet was the most generous amongst the people, and he used to be more so in the month of Ramadan when Gabriel visited him, and Gabriel used to meet him on every night of Ramadan till the end of the month. The Prophet used to recite the Holy Qur'an to Gabriel, and when Gabriel met him, he used to be more generous than a fast wind (which causes rain and welfare).