It is narrated from Sayyidah Aishah (may Allah be pleased with her) that she said: I said: "O Messenger of Allah! Which of your wives will be in Paradise?" He (peace and blessings be upon him) said: "Indeed, you are certainly among them." Sayyidah Aishah (may Allah be pleased with her) said: "The thought came to my mind that this was because he (peace and blessings be upon him) had not married any virgin other than me." This hadith has a sahih (authentic) chain, but the two Shaykhs (Bukhari and Muslim) did not record it.