Matthew 6:34

The reason given is almost comic, and it is meant to be. Don't be anxious for tomorrow, for tomorrow will be anxious for itself.

Tomorrow is personified as perfectly capable of handling its own worrying. It does not need you doing it in advance, and the picture is of a man lying awake doing someone else's job badly. There is a dry humour here that survives translation.

And the argument is practical rather than pious. Jesus does not say worry is faithless, though elsewhere he connects the two. He says it is misallocated. The energy is real and the capacity is limited, and you are spending today's supply on a day that has not arrived and may not arrive in the form you are imagining.

Each day's own evil is sufficient is the line people find bleak, and it should not be softened. He is not saying every day is fine. He is conceding, flatly, that each day contains trouble — enough of it to occupy the resources given for that day. That is a realistic account of life, not an optimistic one.

What it implies is a kind of rationing. Provision, in this sermon, comes daily; so does bread in the prayer he taught a chapter earlier. Anxiety about tomorrow is an attempt to consume a supply that has not been issued yet.