'Rider' in the Bible

Then Moses and the {Israelites} sang this song to Yahweh, {and they said}, "Let me sing to Yahweh because he is highly exalted; [the] horse and its rider he hurled into the sea.

And Miriam answered, "Sing to Yahweh because he is highly exalted; [the] horse and its rider he hurled into the sea."