The Messenger of Allah ﷺ swore that he would not visit his wives for a month. He remained away for twenty-nine days, and on the evening of the thirtieth he came in to me.I said, "You swore that you would not come to us for a month."He replied, "The month is like this," and he extended his fingers three times, "and the month is like this," extending all his fingers but holding back one finger on the third time.
حدثنا هشام بن عمار حدثنا عبد الرحمن بن أبي الرجال عن أبيه عن عمرة
أقسم رسول الله ﷺ أن لا يدخل على نسائه شهرا فمكث تسعة وعشرين يوما حتى إذا كان مساء ثلاثين دخل علي فقلت إنك أقسمت أن لا تدخل علينا شهرا فقال الشهر هكذا يرسل أصابعه فيها ثلاث مرات والشهر هكذا وأرسل أصابعه كلها وأمسك إصبعا واحدا في الثالثة
[Its chain of transmission is hasan]. Ahmad reported it, 6/105, from the hadith of Abdul-Rahman bin Muhammad bin Abdul-Rahman bin Abu Rijal, with this chain. Busiri said, its chain of transmission is hasan. Abdul-Rahman bin Abu Rijal is trustworthy, the majority declared him trustworthy, and no one has criticized him with any valid argument. The transmission from Abu Dawud is not established, because of the unknown status of Ajurri, who narrated from him.