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'". (PT)
English reference (PT): Book 42, Hadith 288 (PT)
Arabic reference (PT): Book 43, Hadith 305 (PT)