Sahih Bukhari
Volume 1, Book 1, Number 5:
Narrated Ibn 'Abbas:

Allah's Apostle was the most generous of all the people, and he used to reach the peak in generosity in the month of Ramadan when Gabriel met him. Gabriel used to meet him every night of Ramadan to teach him the Qur'an. Allah's Apostle was the most generous person, even more generous than the strong uncontrollable wind (in readiness and haste to do charitable deeds).