Musnad Ahmad 30:3376

Yazid narrated to us, Muhammad informed us, from Abu Salamah, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not undertake a journey except to three mosques: the Sacred Mosque (al-Masjid al-Haram), this mosque of mine, and the Al-Aqsa Mosque."