Is the Hadith: "The Messenger of Allah, peace and blessings be upon him, used to fast three days of every month, and sometimes he would delay that until the fasting of the year accumulated for him, and he would then fast Sha'ban," authentic?

The aforementioned hadith has a weak chain of narration (isnad) due to Muhammad ibn Abd al-Rahman ibn Abi Layla's poor memory and inconsistencies in his narrations. Scholars have differed regarding the reason for the Prophet's abundant fasting in Sha'ban. The most sound opinion is that it is a month people tend to overlook, falling between Rajab and Ramadan, and in it, deeds are raised to the Lord of the worlds. The Prophet (peace be upon him) loved that his deeds be raised while he was fasting.