Musannaf Ibn Abi Shayba 3:5162

Ibn ‘Uyaynah narrated to us, from ‘Amr, from Talq, from Qaza‘ah, who said: I asked ‘Umar, "Should I go to Mount Tur?" He said, "Leave Mount Tur and do not go to it." And he said, "Do not undertake a journey except to three mosques."