Musnad Ahmad 25:863

Ishaq—who is Ibn Isa—narrated to us, Muhammad ibn Thabit al-Abdi narrated to me, from Jabalah ibn Atiyyah, from Ishaq ibn Abdullah ibn al-Harith, from Ibn Abbas, who said: While the Messenger of Allah (peace and blessings of Allah be upon him) was in the house of one of his wives, he laid his head down and slept, then he laughed in his sleep. When he awoke, one of his wives said to him: "You laughed in your sleep, so what made you laugh?" He said: "I am amazed by people from my nation who ride this sea, fearing the enemy, striving in the way of Allah." And he mentioned much good for them.