The 'therefore' here seem to point back to the singleness of eye and one master service preciously discussed. The key verse appears to be the 'seek ye first'. If you seek the food and raiment first then the worry for it becomes your master. It is not that you don't need these things for the Father knows that you have need of these things. It is not that the birds do go about the task of seeking out a field in which to eat, it is that it doesn't worry them. Serving two masters makes us to hate the one (most likely our Father) should the worry consume us.
2012 - pBiblx2 Field Wise Bible System Version 2.0.9d - GPL3