Jesus makes at least two points about worry when he talks about it in the Sermon on the Mount (Matthew 6:25-36). He tells us not to worry because worry is ineffective and unnecessary.

Worry doesn't do anything to change the thing you're worrying about. It's ineffective. "Can all your worries add a single moment to your life?" (Matthew 6:27 NLT) Here Jesus references a physical unit of measurement, the cubit (about 18 inches). In other words, If your life span could be measured as with a ruler, and the power of all your worries was applied, the length wouldn't be extended by a single unit. The contrast between the sum total "all" of our worries and their inability to move the needle a "single" tick stands out to me. Worry is ineffective.

But beyond being ineffective, it's unnecessary. To make this point, Jesus draws on common everyday observable facts to draw a logical conclusion: if something is true for these lesser things, it will certainly be true for these more important things. Birds are not particularly valuable animals, but God feeds them. Wildflowers are transient and temporary, but God clothes them with splendor. And in both cases it happens without the need of their labor or initiative. If he feeds and clothes these, he will certainly feed and clothe his far more valuable and lasting people. So our worries are unnecessary.

These are observable facts and logical conclusions, which lead us to trust our heavenly Father. Don't worry, he says. It's ineffective and unnecessary, for "your heavenly Father already knows all your needs." (Matthew 6:32 NLT)