I asked `Aisha "Did Allah s Apostle, use to choose some special days (for fasting)?" She replied, "No, but he used to be regular (constant) (in his service of worshipping). Who amongst you can endure what Allah's Messenger (ﷺ) used to endure?"
Sahih al-Bukhari Book 30, Hadith 94
← Previous Hadith The Prophet (ﷺ) visited her (Juwairiya) on a Friday and she was fasting. He asked her, "Did you fast yesterday?" She said, "No." He said, "Do you intend to fast tomorrow?" She said, "No." He said, "Then break your fast." Through another series of narrators, Abu Aiyub is reported to have said, "He ordered her and she broke her fast."

Sahih al-Bukhari Book 30, Hadith 93 Next Hadith → "While the people were with me on the day of `Arafat they differed as to whether the Prophet (ﷺ) was fasting or not; some said that he was fasting while others said that he was not fasting. So, I sent to him a bowl full of milk while he was riding over his camel and he drank it."

Sahih al-Bukhari Book 30, Hadith 95