When Muhammad hit his wife

This is a hadith going back to Aisha:

[...] When it was my turn for Allah's Messenger (may peace be upon him) to spend the night with me, he turned his side, put on his mantle and took off his shoes and placed them near his feet, and spread the corner of his shawl on his bed and then lay down till he thought that I had gone to sleep. He took hold of his mantle slowly and put on the shoes slowly, and opened the door and went out and then closed it lightly. I covered my head, put on my veil and tightened my waist wrapper, and then went out following his steps till he reached Baqi'. He stood there and he stood for a long time. He then lifted his hands three times, and then returned and I also returned. He hastened his steps and I also hastened my steps. He ran and I too ran. He came (to the house) and I also came (to the house). I, however, preceded him and I entered (the house), and as I lay down in the bed, he entered the (house), and said: Why is it, O 'Aisha, that you are out of breath? I said: There is nothing. He said: Tell me or the Subtle and the Aware would inform me. I said: Messenger of Allah, may my father and mother be ransom for you, and then I told him (the whole story). He said: Was it the darkness (of your shadow) that I saw in front of me? I said: Yes. He struck me on the chest which caused me pain, and then said: Did you think that Allah and His Apostle would deal unjustly with you? She said: Whatsoever the people conceal, Allah will know it. He said: Gabriel came to me when you saw me. He called me and he concealed it from you. [...]

--Sahiih Muslim, Book 4, No 2127