Sahih Bukhari Volume 6, Book 60, Hadith Number 415.

Narrated By Um Atiya : We took the oath of allegiance to Allah’s Apostle and he recited to us:

‘They will not associate anything in worship with Allah,’ and forbade us to bewail the dead. Thereupon a lady withdrew her hand (refrained from taking the oath of allegiance), and said, “But such-and-such lady lamented over one of my relatives, so I must reward (do the same over the dead relatives of) hers.” The Prophet did not object to that, so she went (there) and returned to the Prophet so he accepted her pledge of allegiance.