Yusayr bin Amr narrates from Sahl bin Hunayf (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) inclined his hand towards Madinah and said: "It is a sacred and safe place."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9966