His fast is invalidated whether the vomit returns by itself, or he brings it back intentionally, or the vomit comes out and does not return, nor does it return by itself. There is no need to differentiate between returning and bringing back; he has broken his fast merely by the exit of the vomit. It is a condition for the vomit that invalidates the fast to be intentional and to fill the mouth, and here both conditions are met, thus it invalidates the fast. Refer to Tabyin 1: 325-326, and Radd al-Muhtar 2: 111.