Luke 12:26

“If then you are not able to do even that which is least, why are you anxious concerning the rest?”

So as they cannot do even what is least, add a tiny amount to their length of life (or to their height), why should they spend all their lives worrying about the rest, like the rich fool did, even though he had so much? Worrying about food and clothing is foolish. What they should rather be concerned with is making the most of their lives, of what they themselves are.

It should again be noted that the words are addressed to those called to follow Him. He is not decrying general provision of crops and working on the land, He is speaking of a concern that interferes with their spiritual lives. Having done what they can they must trust God and not worry all the time about such things, for those things are not what should be their main concern.