How should Luke 15 be understood in the overall flow of Scripture?
Luke 15 should be understood within the overall flow of Scripture as Christ dealing with the nation of Israel under the Law and covenants. The temple still operated, and Christ was proving who He was to Israel. The parable of the lost sheep addresses Israel, and the popular song's picture of the ninety-nine safely in the fold is mistaken.
Les explains that Luke 15 is often totally confused, and he gives a song writer part of the blame. The song says the ninety and nine safely lay in the shelter of the foal, but the text has the shepherd leaving them in the wilderness to go after the one lost sheep. Les points out that people often carry a kindergarten Sunday school picture, just as they do with the ark, and that same wrong impression affects this parable. Great moral lessons and applications can be drawn, but for understanding the flow of Scripture, this is still all part and parcel of God's dealing with the nation of Israel under those covenants. Christ is dealing with Israel under the Law, the temple is operating, nothing has been said about not keeping temple worship, and He is still proving to the nation who He is.