John Calvin Commentary Matthew 6:27

"And which of you by being anxious can add one cubit unto the measure of his life?" — Matthew 6:27 (ASV)

Which of you by anxious care, etc.? Here our Lord condemns another fault, which is almost always connected with immoderate anxiety about food: and that is, when a mortal man, claiming more than he has a right to do, does not hesitate, in sacrilegious daring, to go beyond his limits.

“O Lord, I know (says Jeremiah) that the way of man is not in himself it is not in man that walketh to direct his steps,” (Jeremiah 10:23).

You scarcely find one person in a hundred who does not venture to make any promises he sees fit, relying on his own industry and power. The consequence is that those who take credit for themselves for their prosperity do not hesitate to lose sight of God when they enter into any undertaking.

To restrain this mad rashness, Christ tells us that whatever contributes to the support of our life depends wholly on the blessing of God. The meaning is: “It is foolish for men to weary themselves, because all our labors are unnecessary and fruitless, and all our anxieties are to no purpose, unless God blesses them.”

This is more clearly expressed by Luke: If you cannot do even that which is least, why are you anxious about the rest? These words plainly show that Christ reproves not only distrust but also pride, because men ascribe much more than they ought to their own skill.