It was narrated that Ibn ‘Abbas (رضي الله عنه) said:

Whilst the Messenger of Allah (ﷺ) was in the house of one of his wives, he lay down his head and slept, and he smiled in his sleep. When he woke up, one of his wives said to him: You smiled in your sleep; what made you smile? He said: “I am amazed by people among my ummah who will travel by sea to face the enemy, striving in jihad for the sake of Allah.” And he said many good things about them.