What is the ruling on fasting the 13th, 14th, and 15th of Sha'ban, and is it an innovation?

Fasting the three mentioned days of each lunar month is a Sunnah and is not exclusive to the month of Sha'ban. As for singling out Sha'ban for fasting these days, there is no sound evidence for it from the Prophetic Sunnah or the practice of the Companions. It has been reported from some of the Salaf that they observed the night of mid-Sha'ban with abundant worship. However, it is safer for a Muslim to follow the Sunnah of the Prophet, peace and blessings be upon him, and to avoid doubtful matters. If one wishes to fast the White Days, then let him fast them with the intention of fasting the White Days.