It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "When one of you visits his Muslim brother and wishes to break his fast, let him break it, unless that fast of his is of Ramadan, or a make-up of Ramadan, or a vowed fast."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13349