Looking at the birds, because they search for food, we think that they find their food when searching for it. And yes they do but in reality God provides that food for them. Yes God has promised us to clothe us, but he will not put the clothes on us, we do.
People who do not believe in God are worried about food because they do not know that God feeds us – verse 30. But we do and glory and thanks to our Lord Jesus for that! All we need will be given to us by God – verse 31. We do not earn it. He gives it to us.