Yahya related to
me from Malik that he had heard that Said ibn al-Musayyab said, "When
a man comes to his wife in her room, he is believed. When she comes to
him in his room, she is believed."
Malik commented, "I think
that this refers to sexual intercourse. When he comes in to her in her
room and she says, 'He has had intercourse with me' and he says, 'I
have not touched her', he is believed. When she comes in to him in his
room and he says, 'I have not had intercourse with her' and she says,
'He had intercourse with me', she is believed."
Muwatta Malik Book 28, Hadith 14