Wills (Kitab Al-Wasaya)
Dawud :: Book 17 : Hadith 2860
Narrated AbuSa'id al-Khudri:
The Prophet (peace_be_upon_him) said: A man giving a dirham as sadaqah (charity) during his life is better than giving one hundred dirhams as sadaqah (charity) at the moment of his death.