Musnad Ahmad Hadith 7963

It is narrated from Abu Huraira (may Allah be pleased with him) that once the Noble Prophet (ﷺ) left his pure wives (for a month). Umar (may Allah be pleased with him) came to the service of the Noble Prophet (ﷺ) at that time, and the Noble Prophet (ﷺ) was sitting in a room on a mat, the marks of which had appeared on the blessed back of the Noble Prophet (ﷺ). Seeing this, he said, "O Messenger of Allah, (Caesar and) Chosroes drink water in vessels of gold and silver, and you remain in this condition?" The Noble Prophet (ﷺ) said, "Those people have been given good things quickly in this worldly life." Then the Noble Prophet (ﷺ) said, "Sometimes the month is also of twenty-nine days, this much, this much," and the third time he folded his thumb.