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