Jesus has finished giving us illustrations from nature on how God takes care of his creatures. He then reiterates what he said earlier in verse 25 about not being anxious for food, drink or clothing, this time pointing out that the Gentiles are the ones who seek after these things.
Why do the Gentiles behave this way? Because they don't know the true God. They don't have a relationship with the one who commanded the whole world into existence, nor do they know him as "Father." So of course they live in anxiety and spend their lives hording and toiling and amassing resources to ensure their own survival. But if you do know the true God as your Father, you should behave accordingly. Anxiety about bodily needs is for godless people, but for a child of God to behave that way is totally inappropriate. It's like saying you don't have a heavenly Father. It's behaving like a Gentile.
Jesus goes on to say, "For your heavenly Father knows you need these things." I view this as one of those gracious understatements you make when someone practically insults you with their low expectations about your capabilities. "Um, I do know how to tie my own shoes." "Yes, I know how to spell my own name." "I know my right hand from my left, thanks." Jesus may well have said, "Since your heavenly Father did create the world, knows all things from the beginning to the end of time, and sustains the breath of every living thing by the pleasure of his will, I'm sure he is aware of your basic need to eat, drink and put stuff on." I sense that Jesus is being a little stern with us when he says, "O men of little faith!" but he's nowhere near as indignant as he could be considering that our anxiety reflects our tremendously low expectations of God.
But what is all this teaching about anxiety over God's provision leading to? Living healthier and happier lives? Having a positive outlook that wins friends and influences people? Managing money God's way? Actually it's this: "Seek first his kingdom and his righteousness and all these things will be added to you." The assurance that God is taking care of you frees you up to seek first his kingdom. What's the connection? Well, when you think about it seeking first God's kingdom means putting God first, and putting God first means putting the needs of others first--your family, your friends, your church, your neighbors. You serve God through serving his people. Jesus says that to the extent that you minister to the least of his brothers who are among the hungry, the sick, the naked and the imprisoned, you have done so to him. In short, seeking first the kingdom means you have to give.
The reason we don't give is that we think we can't afford to give. Instead of being willing to see how much God will provide when we do step out in faith to give, we tend to shrink back. We immediately became worried we won't have enough left for ourselves. Here's the proof: as soon as Jesus asks us to "freely give" and "seek ye first" what's the first thing we imagine? Ourselves homeless and destitute on the streets all because we followed Jesus' dumb advice. Our minds run to the most extreme scenario and use that as an excuse to justify our disobedience.
But the reality is that most of us will never end up that bad off. And those of us who are experiencing financial problems could probably get it solved by giving more and letting God "add all these things to you." Seeking first the kingdom is what ensures that you will be provided for. Seeking first yourself ensures only anxiety and warring against the God who alone can give you the security you desire.