Moses had seen many lives swept away, leaving graves scattered through the wilderness. The lives of the Israelites were no more durable than grass, covered in dew in the morning and withered and dead by dusk. This was not just due to the inevitable ending of lives but because Israel had rebelled against Yahweh and scorned the covenant, despite all the signs and wonders given to them.
5 You sweep them away as with a flood; they are like a dream, like grass that is renewed in the morning: