Narrated Abdullah ibn Masud: We kept fast for twenty-nine days along with the Prophet ﷺ more often than we kept fast for thirty days.
Related hadith on this topic
Explanation & Benefits
Shaykh Umar Farooq Saeedi
Benefits and Issues:
➊ Twenty-nine fasts, in terms of overall reward, are like thirty, because the foundation of this action is sincerity and obedience.
➋ In (lama sumna), "ma" is either a relative pronoun or a verbal noun.
(: Awn al-Ma‘bud)
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 2322