Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: A man came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah, I wish to go on campaign in the path of Allah. He (peace and blessings be upon him) said: "Hold fast to al-Sham, for Allah, the Mighty and Majestic, has guaranteed al-Sham and its people for me. And of al-Sham, hold fast to Asqalan, for when the millstone (of tribulation) turns in my Ummah, its people will be in goodness and well-being."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11103