Abu Hurayrah Radhiyallahu anhu says:
"Rasulullah sallallahu alayhi wasallam said: 'Deeds are presented (before Allah subhanahu wata'allah) on Mondays and Thursdays. I desire that my deeds be presented whilst I am fasting'". (FR)
English reference (FR): Book 42, Hadith 288 (FR)
Arabic reference (FR): Book 43, Hadith 305 (FR)