All of his past sins forgiven
It is narrated on the authority of Abu Hurayrah رضي الله عنه that the Prophet صلي الله عليه وسلم said :
“He who observes the fast of the month of Ramadhaan out of sincerity and hope for the reward from Allaah will have his past sins forgiven.”
Saheeh Al- Bukhaari (Arabic/English), vol. 3, # 125.