What is the ruling on fasting six days of Shawwal after Ramadan, knowing what has been reported from Imam Malik in his Muwatta' concerning his disapproval of it for fear of it being an innovation?

It has been authentically narrated from Abu Ayyub that the Prophet, peace and blessings be upon him, said: "Whoever fasts Ramadan and then follows it with six days of Shawwal, that is like fasting for a lifetime." This is an authentic hadith indicating the Sunnah (recommended practice) of fasting six days of Shawwal. Imam Shafi'i, Imam Ahmad, and a group of other imams acted upon it. This cannot be opposed by mere conjectures, such as the fear that an ignorant person might believe it is part of Ramadan or might think it is obligatory, because conjectures cannot stand against an authentic Sunnah.