As-Salamu `Alaykum Wa Rahmatullahi Wa Barakatuh akhi,
This Hadith is in Sahih Al Bukhari.
As I mentioned before, Maria was either the wife or concubine of the Messenger of Allah (may Almighty Allah bless him and grant him peace) so it is Islamically allowed in both cases to have sex with her.
The thing is, Prophet Muhammad (may Almighty Allah bless him and grant him peace), despite what the enemies of Islam say, was the most kind hearted and thoughtful man to ever walk the Earth. He knew how Hafsa felt and became fully aware of what he did. It is lawful in Islam to have sex with your wives or concubines, and it is lawful to marry up to four wives as long as you can be fair between them. This is mentioned in the Glorious Qur'an. He loved all his wives and was equal in treating them all. Afterall, he is a human being and no human is perfect and faultless, but he was without a doubt the closest anybody could ever get.
I don't know what the Islamophobes try to point out playing with the wording in most Hadiths and Qur'anic verses and giving people a negative impression on Islam, but as long as you yourself are sure that Allah, the Most Glorified and Exalted, is the One and Unique God, and that Prophet Muhammad (may Almighty Allah bless him and grant him peace) is truly the Messenger of the Almighty, and that Islam is the true path to success and to Paradise, you should not even care about what they say. They try so hard to prove Islam wrong even if it were by a mere letter in the Glorious Qur'an but epically fail, whereas they never even open their eyes and see the 101 faults in the religion they follow, that is if they even do follow one in the first place.
