Yahya bin Amr bin Salamah (may Allah have mercy on him) narrated from his father: Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) was asked about perpetual fasting (fasting the whole year), and he disliked it and said: "Fasting three days of every month (is sufficient)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8951