The book of Philemon is unique in many respects. The shortest of Paul’s inspired writings, it is the only one of the prison epistles addressed to an individual. Although it does not reach the lofty doctrinal heights of the others (Colossians, Philippians, and Ephesians), it does deal with a vitally important practical issue. Paul takes the truth that Christians are to forgive each other (cf. Ephesians 4.32; Colossians 3.13), first taught in the New Testament by our Lord Himself in the gospel of Matthew, and applies it to a specific situation.
The Bible clearly teaches the wonderful truth that God is a forgiving God. In Exodus 34.6-7, God described Himself to Moses as “the Lord, the Lord God, compassionate and gracious, slow to anger, and abounding in lovingkindness and truth, who keeps lovingkindness for thousands, who forgives iniquity, transgression, and sin.”
That theme runs throughout Scripture (cf. Psalms 32.1; 85.23; 130.3-4; Isaiah 43.25; 55.7; Jeremiah 33.8; Ephesians 1.7; Colossians 1.14; 1 John 1.9; 2.12), but it is, perhaps, nowhere better illustrated than in the story of the prodigal son (Luke 15.11-32). A father had two sons, one of whom took his share of the inheritance and left home (verses 11-12). After living a debauched life until his money ran out, the one son was forced to take a menial job (verses 13-16). He finally came to his senses and exclaimed, “How many of my father’s hired men have more than enough bread, but I am dying here with hunger!” (verse 17). He decided to return to his father (verse 18), but apparently did not expect forgiveness. He hoped merely to be tolerated (verse 19). But the father did not wait for his sinning son to reach him. While his son was still a long way away, he ran to him and embraced him (verse 20). Later, he threw a party to celebrate his son’s return (verses 22-24).
That story illustrates how God, represented in the story by the father, forgives: eagerly, totally, lavishly. We could say, in a sense, that God is never more like Himself than when He forgives.
From: The MacArthur New Testament Commentary: Colossians and Philemon (Volume 22) by John MacArthur (Chicago: Moody Publishers, 1992), pp. 201-202.