"For I am the least of the apostles, unworthy to be called an apostle, because I persecuted the church of God."
1 Corinthians 15:9 ESV
"To me, though I am the very least of all the saints, this grace was given, to preach to the Gentiles the unsearchable riches of Christ..."
Ephesians 3:8 ESV
"The saying is trustworthy and deserving of full acceptance, that Christ Jesus came into the world to save sinners, of whom I am the foremost."
1 Timothy 1:15 ESV
As Paul continues his journey in ministry and faith, a pattern can be noticed when considering his epistles in chronological order. The more Paul matures in faith, the lower he sees himself - the more he can see that he is a sinner who needs saving.
This is not saying that Paul is becoming more sinful. Instead, Paul is progressively adjusting to reality and understanding it. Christian, the more you mature in Christ, the greater you shall see sin in your life, and all the more shall you realise (even though you do not deserve it) you need a Saviour!
Let this become a way to glorify our Lord who has bore our sin and took the punishment that we deserve. Let us deepen the way we appreciate and glorify God the more mature we become in Christ.
Amazing grace, indeed, how sweet the sound!