Charles Ellicott 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)

One cubit unto his stature — The Greek word for “stature” can mean either physical height (as in Luke 19:3, and perhaps Luke 2:52) or lifespan (as in John 9:21, 23, and Hebrews 11:24). Either meaning provides a suitable interpretation for the passage. No anxiety will alter our physical height, and since the other conditions of our life are just as fixed by God’s laws, they are equally independent of our will. Neither will that anxiety add to the length of life God has appointed for us.

Of the two meanings, however, the latter (lifespan) best satisfies the teaching of the context. People are not anxious about adding to their stature; they are, however, often anxious about prolonging their life. If we accept the thought that our days are but as a span long (Psalms 39:5), then the addition of a cubit becomes a natural metaphor. It should be noted that in the parallel passage in St. Luke (Luke 12:26), this appears as that which is least, and which yet lies beyond our power.