Why are some Christians stable and productive, but others are uncertain and confused?  Those who base their lives on lies, fleshly energy and human wisdom end up in confusion (James 3:14-16).  Those whose hearts are stabilised on God’s truth and grace in Christ experience confidence (1 Peter 1:13).  Peter now summarises the purpose of his letter: to encourage stability based on truth, freedom based on God's grace through Christ, and perseverance encouraged by the Scriptures (Romans 15:4).
 
The apostles understood that to be part of Christ's church they needed to be in fellowship with like-minded believers.  Silas has been a faithful companion and 'armour bearer' (1 Samuel 14:6-7) to Paul (Acts 15:40), and now to Peter.  Both valued the gracious and courageous fellowship of this man, who probably wrote as Peter dictated the letter.  Even the most powerful of God's servants is weak without the encouragement of Godly fellowship (2 Corinthians 2:13). The faithfulness of Silas was not just personal loyalty (Acts 15:26), although that is an essential part of any ministry team; but he could be trusted to fully participate in the gospel work, because he also trusted the faithfulness of God to him (Acts 16:25).

“Stand fast” is a military term that means refusing to give ground to the enemy.  Paul’s instructions were the same, “Therefore put on the full armour of God, so that when the day of evil comes, you may be able to stand your ground, and after you have done everything, to stand. Stand firm then …” (Ephesians 6:13-14).  This is not an instruction to advance, but simply to stand while the enemy throws his worst at you – but being confident that you are protected by God.  Do not run away.  Just stand, shielded by God’s power (1 Peter 1:5).
 
Encouragement is very important.  This letter has already explained how easily Satan can discourage us: so let us encourage others to stand firm in the grace of Jesus Christ, and urge one another to live in a way that glorifies Him.  Even if encouragement is unusual in your culture, be radical and find a good reason to spur on your brothers and sisters in Christ to love and good deeds (Hebrews 10:24).  It is not easy to follow Jesus, particularly in the workplace or where people are hostile to you because of your faith; so we need the encouragement of the Holy Spirit, the Scriptures and other believers.  And they need you!  Seek them out; and build them up by your example, prayers and teaching.