It originates from the Bible, specifically from the Book of Exodus, where the Israelites are promised a land flowing with "milk and honey". This symbolizes a land of plenty, where their needs will be met and they will live in peace and comfort.
Examples of how it's used:
* "After years of struggle, they finally entered a period of days of milk and honey."
* "The company's recent success has brought them days of milk and honey."
* "We're all enjoying the days of milk and honey, but we shouldn't forget that things can change."