The ruling on the obligation of persisting in voluntary fasting for one who fasts

Question:
In one of them, she says: I have heard that the one who wants to fast six days of Shawwal voluntarily, as well as the three white days—the 13th, 14th, and 15th—is required to persist in that. Is what was said correct?

Answer:
In the name of Allah, the Most Gracious, the Most Merciful. Praise be to Allah, and may Allah send blessings and peace upon His Messenger, his family, and his Companions, and upon those who follow his guidance. As for what follows, fasting the six days of Shawwal, and likewise the white days, and likewise Monday and Thursday, are all sunnah (recommended practice), all mustahabb (recommended) voluntary acts. Whoever fasts them and persists in them has his reward, and whoever fasts them at times and leaves them off at other times has his reward. It is not obligatory to persist in them.
The one who says that persisting is obligatory has erred. Rather, it is up to the Muslim: when it is easy for him, he fasts, and when he is occupied with other matters, he breaks the fast. The Prophet (peace and blessings be upon him) would sometimes fast consecutively until it was said he does not break the fast, and sometimes he would break the fast consecutively until it was said he does not fast, due to considering his engagements and the absence of engagements. So when he was free, he would fast consecutively, and when he was occupied, he would break the fast, peace and blessings be upon him.
In summary, it is not obligatory for the believer to persist in the six days or the white days. Rather, when it is easy for him, he fasts them, and if he leaves them off, there is no blame on him, and praise be to Allah. Likewise, if he fasts Monday and Thursday and leaves them off at times, there is no blame. They are all a blessing for him, and praise be to Allah.