Volume 7, Book 62, Number 129:
Narrated Anas:
Allah’s Apostle took an oath that he would not visit his wives for one month, and he sat in an up –
per room belonging to him. Then, on the twenty ninth day he came down. It was said, “O Allah’s
Apostle! You had taken an oath not to visit your wives for one month.” He said, “The (present) month
is of twenty-nine days.”