Musnad Ahmad 32:1412

Abu al-Yaman narrated to us, he said: Isma'il ibn 'Ayyash narrated to us, from 'Umar ibn Muhammad, from Abu 'Iqal, from Anas ibn Malik, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Ashkelon is one of the two brides. Seventy thousand will be resurrected from it on the Day of Resurrection, upon whom there is no reckoning. And fifty thousand will be resurrected from it as martyrs, as delegations to Allah. In it are the rows of the martyrs, their heads severed in their hands, their jugular veins gushing blood. They say: 'Our Lord, give us what You promised us through Your messengers; indeed, You do not break the promise.' He will say: 'My servants have spoken the truth. Wash them in the River of Al-Bayda.' So they will emerge from it pure and white, and they will roam in Paradise wherever they wish."