This proves that late in his life as an apostle, Paul was still keenly aware of the enormity of what he had been forgiven. He probably purposely kept this memory alive so as not to take any chance of losing his sense of responsibility. He understood human nature well, not wanting to risk losing the proper perspective that Christ had given him at the beginning. Rather than carry it about as a burdensome load of guilt, he used it as a realistic recognition of his indebtedness to Christ for what he had been forgiven and what had been accomplished since that time.
John W. Ritenbaugh
An Unpayable Debt and Obligation
Paul uses himself to exemplify the great magnitude of Christ's patience toward us. "Longsuffering" strongly implies forbearance under great duress. As Paul describes it, he had not just sinned in blaspheming and inflicting injury on the saints, but he had done his deeds with a proud, haughty, arrogant, and insolent spirit. He acted in a wicked, malicious, violent way—a spirit of tyranny that greatly aggravated the wrong he did. Other translations render insolent as "insulter," "insolent foe," "oppressor," "wanton aggressor," "doer of outrage," and "wanton outrage."
Paul's aim is to magnify Christ's patience and forgiveness as an example to himself and his audience. The apostle followed Christ's example by in turn exercising patience toward the church. Considering his own circumstance, he undoubtedly felt strongly about this because Christ's forbearance with him opened salvation to him. In response, he passes it on to Timothy and so to us.
In II Timothy 4:2-3, Paul exhorts the evangelist to use this virtue that means so much to our salvation:
Preach the word! Be ready in season and out of season. Convince, rebuke, exhort, with all longsuffering and teaching. For the time will come when they will not endure sound doctrine, but according to their own desires, because they have itching ears, they will heap up for themselves teachers; and they will turn their ears away from the truth, and be turned aside to fables.
John W. Ritenbaugh
The Fruit of the Spirit: Patience