The Messenger of Allah ﷺ struck one hand against the other and said, "The month is like this, and like this," then on the third time he held back one finger.
ضرب رسول الله ﷺ بيده على الأخرى، فقال: الشهر هكذا وهكذا ثم نقص في الثالثة إصبعا.
Muslim narrated it in the Book of Fasting (1086) via Ismail bin Abu Khalid, who said, "Muhammad bin Saad narrated to me, from his father, Saad bin Abu Waqqas," and he mentioned it. In another version of his, the wording is, "The month is like this, and this, and this, ten and ten and nine once."