20 The bed is too short to stretch out on, the blanket too narrow to wrap around you.

Read Isaiah 28:20 Using Other Translations

For the bed is shorter than that a man can stretch himself on it: and the covering narrower than that he can wrap himself in it.
For the bed is too short to stretch oneself on, and the covering too narrow to wrap oneself in.
The bed you have made is too short to lie on. The blankets are too narrow to cover you.