Take therefore no thought for tomorrow: for tomorrow shall take thought of the things for itself. Sufficient unto the day is the evil thereof.
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Augustine of Hippo
With a single heart, therefore, and exclusively for the sake of the kingdom of heaven, we ought to do good to all. And in this welldoing we ought not to think about temporal rewards, either exclusively or conjointly with the kingdom of God. For it is with reference to all these temporal things that the Lord used the word tomorrow when he said, “Do not think about tomorrow.” For that word is not used except in the realm of time, where the future succeeds the past. Therefore, when we perform any good deed, let us think about eternal things and pay no heed to the temporal. Then our deed will be not only good but also perfect. “For tomorrow,” he says, “will have anxieties of its own.” By this he means that you are to take food or drink or clothing when it is fitting that you do so. When the need for them is pressing, these things will be at hand; our Father knows that we need all these things. “For sufficient for the day,” he says, “is its own evil.” In other words, when the need is urgent, we have sufficient reason for using these things. I suppose that this necessity is called evil because it partakes of the nature of punishment for us since it is part of the frailty and mortality that we have merited by committing sin. To this penalty of temporal necessity, therefore, do not add something more troublesome. .