It is narrated from Sayyiduna Imran bin Husain (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said to a man: "Did you fast at the end of this month?" He replied: No. The Prophet said: "When you have completed the fasts of Ramadan, then keep two fasts at the end of the month." Imam Darimi (may Allah have mercy on him) said: By «سرره» is meant the end of the month.
Hadith Takhrijاس روایت کی سند صحیح اور حدیث متفق علیہ ہے۔ دیکھئے: [بخاري 1983] ، [مسلم 1161] ، [أبوداؤد 2328] ، [ابن حبان 3587]
Brief Explanation
(Commentary on Ahadith 1777 to 1780) Imam Darimi rahimahullah has taken the meaning of «سَرَرُهُ» as the end of the month, while some people have taken it as the beginning of the month, and some as the middle of the month. In some narrations, "Sirr Sha'ban" is mentioned, which, if the end of the month is intended, would conflict with the prohibition in the hadith against fasting one or two days before the arrival of Ramadan. However, if the beginning of the month is intended, then the problem is resolved. (And Allah knows best).