If one fasts voluntarily and then breaks the fast during the day, is making it up obligatory?

The questioner : Some of the scholars say that if he kept him company and the man was his own self, he issued a ruling against him. Is this impossible?

The Shaykh : The correct view is that making it up is obligatory for you. There is no voluntary act that, if you invalidate it, requires you to make it up, except for Hajj and 'Umrah only.

The questioner : And they say this.

The Shaykh : No, no, you did not make a vow. And it will come to us, if Allah wills, when we pass through the beginning of the chapter on the Prophet’s (peace and blessings be upon him) entering upon his family, where it is said that something was gifted to him, and he said, “Show it to me, for I have become a fasting person,” and he ate. But the objectors say, “Fasting” means fasting from food, not a legal fast. It is said that the original principle is that whatever the Messenger (peace and blessings be upon him) uttered is a legal reality. This is the original principle.