(4) باب الشَّهْرِ يَكُونُ تِسْعًا وَعِشْرِينَ
Narrated Abdullah ibn Mas'ud:
We kept fast for twenty-nine days along with the Prophet (ﷺ) more often than we kept fast for thirty days. (ID)
Reference (ID): Sunan Abi Dawud 2322 (ID)
In-book reference (ID): Book 14, Hadith 10 (ID)
English translation (ID): Book 13, Hadith 2315 (ID)