Narrated Aisha:
A necklace of mine was lost at Al-Baida' and we were on our way to Medina. The Prophet (ﷺ) made his camel kneel down and dismounted and laid his head on my lap and slept. Abu Bakr came to me and hit me violently on the chest and said, "You have detained the people because of a necklace." I kept as motionless as a dead person because of the position of Allah's Messenger (ﷺ) ; (on my lap) although Abu Bakr had hurt me (with the slap). Then the Prophet (ﷺ) woke up and it was the time for the morning (prayer). Water was sought, but in vain; so the following Verse was revealed:-- "O you who believe! When you intend to offer prayer.." (5.6) Usaid bin Hudair said, "Allah has blessed the people for your sake, O the family of Abu Bakr. You are but a blessing for them."
USC-MSA web (English) reference: Vol. 6, Book 60, Hadith 132
Arabic reference: Book 65, Hadith 4608