Jesus asked this to free His disciples from anxious worry about food and clothing (Luke 12:22). The rich man had planned to build greater barns (Luke 12:18), but the ravens "neither have storehouse nor barn," and still "God feedeth them" (Luke 12:24). If God feeds birds, He will surely care for His children. Gill notes that ravens were "fowls of very little worth, and disregarded by men," and even "unclean by the law." Barnes, in the Matthew notes to which his Luke note refers, marvels, "How regularly are they fed from the hand of God!"

The answer is so obvious that Jesus moves straight on. He asks which of them by worrying "can add to his stature one cubit" (Luke 12:25-26). He points to the lilies, which God clothes more gloriously than Solomon, and asks, "how much more will he clothe you, O ye of little faith?" (Luke 12:27-28). He assures them, "your Father knoweth that ye have need of these things" (Luke 12:30), and tells them, "seek ye the kingdom of God; and all these things shall be added unto you" (Luke 12:31). He ends, "Fear not, little flock" (Luke 12:32).

Under the Law of Moses, the raven was an unclean bird (Leviticus 11:15), which is Gill's point when he calls it "unclean by the law." Matthew's parallel says "the fowls of the air" (Matthew 6:26), while Luke names the ravens.

In the KJV, "Take no thought" means do not be anxious, as the ESV renders it (Luke 12:22). Gill connects God's feeding of ravens to Job 38:41, where the young ravens cry to God for food; Barnes' references on this verse add Psalm 147:9.

This question shows God as a Father who provides. Jesus does not argue that the disciples should take care of themselves. He points them to what God already does every day for creatures that have no barns at all. Barnes says the purpose of this teaching was "to warn his disciples against avarice, and, at the same time, against anxiety about the supply of their needs." The two belong together: the rich man trusted what he had laid up (Luke 12:19), and the disciples are told to trust their Father, who knows their needs (Luke 12:30).

The passage moves from the rich man's barns to the ravens with no barns, and ends with God's gift: "it is your Father's good pleasure to give you the kingdom" (Luke 12:32). The God who feeds the ravens gives His people far more than food.