Mahdi bin Maymun narrated this hadith with the same chain, that the Prophet (peace and blessings be upon him) said to a man: "Have you fasted at the end of this month?" He said: No (meaning in Sha'ban). He (peace and blessings be upon him) said: "When you have finished fasting, then fast one day or two days."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7968