Jamieson, Fausset and Brown on Matthew 6:27

27. Which of you, by taking thought--anxious solicitude.

can add one cubit unto his stature?--"Stature" can hardly be the thing intended here: first, because the subject is the prolongation of life, by the supply of its necessaries of food and clothing: and next, because no one would dream of adding a cubit--or a foot and a half--to his stature, while in the corresponding passage in Luke (Lu 12:25, 26) the thing intended is represented as "that thing which is least." But if we take the word in its primary sense of "age" (for "stature" is but a secondary sense) the idea will be this, "Which of you, however anxiously you vex yourselves about it, can add so much as a step to the length of your life's journey?" To compare the length of life to measures of this nature is not foreign to the language of Scripture (compare Psa 39:5; 2Ti 4:7, &c.). So understood, the meaning is clear and the connection natural. In this the best critics now agree.