Matthew 6:25

There is scarcely any one sin against which our Lord Jesus more largely and earnestly warns his disciples, or against which he arms them with more variety of arguments, than the sin of disquieting, distracting, distrustful cares about the things of life, which are a bad sign that both the treasure and the heart are on the earth; and therefore he thus largely insists upon it. Here is, I. The prohibition laid down. It is the counsel and command of the Lord Jesus, that we take no thought about the things of this world; I say unto you. He says it as our Lawgiver, and the Sovereign of our hearts; he says it as our Comforter, and the Helper of our joy. What is it that he says? It is this, and he that hath ears to hear, let him hear it. Take no thought for your life, nor yet for your body (Mat 6:25). Take no thought, saying, What shall we eat? (Mat 6:31) and again (Mat 6:34), Take no thought, mē merimnate - Be not in care. As against hypocrisy, so against worldly cares, the caution is thrice repeated, and yet no vain repetition: precept must be upon precept, and line upon line, to the same purport, and all little enough; it is a sin which doth so easily beset us. It intimates how pleasing it is to Christ, and of how much concern it is to ourselves, that we should live without carefulness.

— Matthew Henry's Concise Commentary (public domain)

Therefore I say unto you, Take no thought--"Be not solicitous." The English word "thought," when our version was made, expressed this idea of "solicitude," "anxious concern"--as may be seen in any old English classic; and in the same sense it is used in Sa1 9:5, &c. But this sense of the word has now nearly gone out, and so the mere English reader is apt to be perplexed. Thought or forethought, for temporal things--in the sense of reflection, consideration--is required alike by Scripture and common sense. It is that anxious solicitude, that oppressive care, which springs from unbelieving doubts and misgivings, which alone is here condemned. (See Phi 4:6). for your life, what ye shall eat, or what ye shall drink; nor yet for your body, what ye shall put on--In Luke (Luk 12:29) our Lord adds, "neither be ye unsettled"--not "of doubtful mind," as in our version. When "careful (or 'full of care') about nothing," but committing all in prayer and supplication with thanksgiving unto God, the apostle assures us that "the peace of God, which passeth all understanding, shall keep our hearts and minds in Christ Jesus" (Phi 4:6-7); that is, shall guard both our feelings and our thoughts from undue agitation, and keep them in a holy calm. But when we commit our whole temporal condition to the wit of our own minds, we get into that "unsettled" state against which our Lord exhorts His disciples. Is not the life more than meat--food.

— Jamieson-Fausset-Brown Commentary (public domain)