عن أنس رضي الله عنه أن النبي ﷺ أراد أن يتزوج إمرأة فبعث بإمرأة لتنظر إليها فقال شمي عوارضها وأنظري إلى عرقوبيها قال فجاءت إليها فقالوا ألا نغديك يا أم فلان قالت لا آكل إلا من طعام جاءت به فلانة قال فصعدت في رف لهم فنظرت إلى عرقوبيها ثم قالت قبليني يا بنية قال فجعلت تقبلها وهي تشم عارضها قال فجاءت فأخبرت
السنن الكبرى للبيهقي كتاب النكاح باب ما خص به من أن أزواجه أمهات المؤمنين وأنه يحرم نكاحهن من بعده على جميع العالمين
Anas (may Allah be pleased with him) related that the Prophet (SAW) wanted to marry a certain woman, so he sent another woman out to have a look at her; He said: Smell her cheeks and look at her hamstrings. So this woman went to her; and the people said: Shall we not give you something to eat, oh mother of so-and-so? She said: I do not eat anything but the food that so-and-so brings. Then she got up on a shelf they had and looked at her hamstrings, then said: Come close to me, my dear. So she came and got close to her, and she smelled her cheek. Then she came back and gave the report.
Al-Bayhaqi, Al-sunan Al-kubra [The Greater Compilation of Sunnah], The book of marital relations, Section: what pertained especially to Him in that His wives were the mothers of the believers, and that after Him, marital relations with them were prohibited to the whole world