Jabir reported God's Messenger as saying, “A man must not spend the night in the house of a woman who has been married unless he is her husband or a close relative.”
Abu Sa'id reported God’s Messenger as saying, “A man must not look at a man’s private parts or a woman at a woman’s, and a man must not come close to a man in one garment or a woman to a woman in one garment.”
‘Uqba b. ‘Amir reported God’s Messenger as saying, “Avoid going in where women are.” A man said, “Messenger of God, tell me about the relatives of a woman’s husband,” to which he replied, “The relatives of a woman’s husband are death.”*
*The word "death” is used to indicate a strong prohibition, the idea being that they are a cause of temptation to a man’s wife.
Ibn Mas'ud reported God’s Messenger as saying, “A woman must not come in close contact with another and then describe her to her husband, for that is as if he were looking at her.”