Luke 12:28

“But if God so clothes the growth in the field, which today is, and tomorrow is cast into the oven, how much more will he clothe you, O you of little faith?”

And God supplies such beauty to what grows in the fields in spite of how temporary their lives are. (For ‘today and tomorrow' compare Luke 13:32 where it means for a little while). How much more then will He add to our lives the beauty that we seek, the true beauty, and ensure that we are clothed.

And yet they should then note that all that beauty of the flowers eventually gets burned up as fuel in the ovens. In the end it is really worth nothing. What does matter is the beauty of soul that will survive to eternity.

The reference to the casting into the oven (a beehive shaped oven used for cooking) is a reminder of how transient these beautiful flowers are. They die quickly and are then used for cooking with. Like our own food and clothing, they are temporary and all the beauty that they had was transient. In a moment it was gone. Thus the women who are His disciples should not be spending a lot of time concentrating on their own physical beauty, for it will pass away. What they should be spending their time on is the true beauty that reveals that they are of God (1 Timothy 2:9).

‘O you of little faith.' At the root of all failure to do God's will is a lack of faith. For those who believe have no problem with all this. If we question it, it is not because it is not the rational and logical way for a believer to behave, it is because we are not sure of God.