Mukhtasar Muslim

Narrated from Sayyiduna Uqbah bin Amir (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Avoid going to women. An Ansari man said, "O Messenger of Allah! What about the husband's brother?" The Prophet (peace and blessings be upon him) said, "The husband's brother is death." (Meaning, the real danger is from the husband's brother.) Sayyiduna Laith bin Sa'd (may Allah be pleased with him) used to say that in the hadith where it is mentioned that the husband's brother is death, it refers to the husband's relatives and close ones, such as the husband's brother or his paternal cousin (all those relatives of the husband with whom marriage is permissible for the woman are included among the husband's brothers, and she should observe veiling from them, except for the husband's father, grandfather, or his son, as they are mahram and there is no need to observe veiling from them).