St. Luke did not idly present three parables in a row... The mercy of the divine act is the same, but the grace differs according to our merits. The weary sheep is recalled by the shepherd, the coin which was lost is found, the son retraces his steps to his father and returns, guilty of error but totally repentant.
In chapter 15 Jesus gives three parable teachings to the crowds concerning God's patience and mercy in calling sinners to salvation by using common examples of daily life. The parables are: the Parable of the Lost Sheep (Lk 15:3-8), the Parable of the Lost Coin (Lk 15:8-10), and the Parable of the Lost Son (Lk 15:11-32). Of these three parables St. Ambrose writes: By the parables of the sheep that strayed and was found, the coin which was lost and was found, and the son who was dead and came to life, we may cure our wounds, being encouraged by a threefold remedy. "A threefold cord will not be broken." Who are the father, the shepherd and the woman? They are God the Father, Christ and the Church. Christ carries you on his body, he who took your sins on himself. The Church seeks and the Father receives. The shepherd carries. The mother searches, the father clothes. First mercy comes, then intercession, and third reconciliation. Each complements the other. The Savior rescues, the Church intercedes, and the Creator reconciles (Ambrose, Exposition of the Gospel of Luke, 7.207-8).
JSH+