From Sahih Bukhari (Hadith 5229):
Narrated `Aisha:I never felt so jealous of any wife of Allah's Messenger (ﷺ) as I did of Khadija because Allah's Messenger (ﷺ) used to remember and praise her too often and because it was revealed to Allah's Messenger (ﷺ) that he should give her (Khadija) the glad tidings of her having a palace of Qasab in Paradise
Reference: Bukhari 5229