To be without spot or blemish is to be without moral defect (1 Timothy 6:14; James 1:27), the pursuit of purity in the eyes of God (see also Ephesians 4:3; 2 Timothy 2:15; Hebrews 4:11). This is in direct contrast to the spots and blemishes of the heretics (2 Peter 2:13). This does not mean that believers will be perfect but it emphasizes the godly lives which believers ought to (and increasingly will) lead.1
When it comes to being at peace, there is some debate. Some commentators consider it to be similar to the idea found in 1 Peter 1:19; the objective condition of being reconciled with God (Romans 5:1) and being found acceptable before him (1 Peter 1:2; 1 Peter 5:14; 2 Peter 1:2).2 Others argue that it relates to the community, the church, and the city where Christians live (see 1 Peter 3:11; James 3:18). Being at peace with others is a Christian virtue.3
14 Therefore, beloved, since you are waiting for these, be diligent to be found by him without spot or blemish, and at peace.