34 Be not therefore solicitous for to morrow; for the morrow will be solicitous for itself. . . .
Jerome: Tomorrow in Scripture signifies time future, as Jacob in Genesis says, “Tomorrow shall my righteousness hear me” [Gen 30:33].
Let us leave to God the future which is uncertain. And this is that He says, “The morrow shall be anxious for itself;” that is, it shall bring its own anxiety with it.
Pseudo-Chrysostom: By “today” are signified such things as are needful for us in this present life; “Tomorrow” denotes those things that are superfluous. “Be not ye therefore anxious for the morrow,” thus means, Seek not to have aught beyond that which is necessary for your daily life, for that which is over and above, i.e. Tomorrow, shall care for itself.
34 . . . Sufficient for the day is the evil thereof.
Jerome: By evil He means here not that which is contrary to virtue, but toil, and affliction, and the hardships of life.
Pseudo-Chrysostom: The toil you undergo for necessaries is enough, do not toil for things superfluous.
Augustine: It is enough that necessity shall compel to take these things; He calls it “evil,” because it is penal, inasmuch as it pertains to our mortality, which we earned by sinning. To this necessity then of worldly punishment, add not further weight.
But herein we must be careful, that, when we see any servant of God endeavouring to provide necessaries either for himself, or those committed to his care, we do not straight judge him to sin against this command of the Lord in being anxious for the morrow. For the Lord Himself, to whom Angels ministered, thought good to carry a bag for example sake. And in the Acts of the Apostles it is written, that food necessary for life was provided for future time, at a time when famine threatened.
Scripture from the Douay-Rheims Bible. Commentary from St. Thomas Aquinas, Catena Aurea, Vol. I (London: Rivington, 1842).