The Book of Pilgrimage (Kitab Al-Hajj)
Muslim :: Book 7 : Hadith 3218
Abu Huraira (Allah be pleased with him) reported it directly from Allah's Apostle (may peace be upon him) that he said: Do not undertake journey but to three mosques: this mosque of mine, the Mosque of al-Haram and the Mosque of Aqsa (Bait al-Maqdis).