"For this reason I say to you, do not be worried about your life, as to what you will eat or what you will drink; nor for your body, as to what you will put on. Is not life more than food, and the body more than clothing? (Matthew 6:25 NASB)
The first thing to notice in this text is the transition 'For this reason I say to you...' which is a clear indication that this verse (6:25) is the next logical step from the preceding verse which reads: "No one can serve two masters; for either he will hate the one and love the other, or he will be devoted to one and despise the other. You cannot serve God and wealth." In other words; because you cannot serve two masters... do not be worried about your life.
Serving two masters will lead to anxiety and insanity, but the very opposite is true when you serve one master, assuming the master is kind and not derelict. Anything that I own, I am responsible for and have to answer for. If I own a house and it is a mess and falling apart I am the one to blame for neglecting it, if I have a pet dog that starves to death, I am the one responsible for not feeding it, if I have a car that runs out of gas, I am responsible for not filling it up and so on. Now with that in mind, my own possessions reflect my character, if have been given much and neglect all of it, people could look at me and rightly assert that I am lazy, incompetent, and so on. Now, a master owns his slave, moreover the master's reputation as a good man, a caring man, a moral man, rides on his treatment of that slave. If a master constantly abuses a slave, does not feed that slave, and never provides for that slave you would be right in saying that he is a harsh master and a bad man. However if the master cares for the slave, yea even takes the slave in and effectively considers him as a son, then that master gets great honor and glory as a 'good man'. Moreover, because the master is good, the slave has nothing to worry about, except to do the master's will, because the good master will take care of everything else.
The parallel is obvious here, and the connection between the Father as a good master, and us as His servants needs little mention. The implications are huge though. I want to be careful how I say this so as not to be blasphemous, but in a very real sense God's glory is tied and even (in a sense) dependent upon the believers provision. Now be very careful here, God does not need to provide you anything to be God, or to be glorious. However at the same time, if indeed you God has claimed you as His servant, if He does not provide your basic needs He has proven Himself to be an unworthy master. So therefore, servant of the King, do not be worried about food or drink, or clothing, or shelter, that is the business of the master to take care of, and rest assured you have a wonderful master if indeed your master is the most High God.
A word must be said here so that you do not get the idea that Christ is teaching some bogus prosperity teaching about how as a believer you should have a big home, a Mercedes Benz, and so on. He is teaching that you will have clothing, shelter, and food... and freedom from the worry concerning those items. In fact in most cases if the Lord were to bless a servant with much riches the servant would come to believe himself to be the master because of his own wealth. Thus it is harder for a camel to get through the eye of a needle than a wealthy man to enter into heaven...
The foundation for the freedom from worry is confidence in the character of God as a master to provide for you, His slave.