Having addressed each of the household relationships (3:18-4:1), Paul now turns his attention back to the whole church. He gives his final exhortations.
Prayer (2): We devote ourselves to prayer and maintain spiritual alertness in it. The former is what Christ called for (Lk. 11:5-9; 18:1) and exemplified (Lk. 5:16; Mk. 1:35), and the first church practiced it (Acts 2:42)! The latter shows that our spiritual vigilance is tied to prayer. Without prayer you're sure to be spiritually drowsy! Christ won for us on the cross an open access to the holy God (Heb. 10:19). With thanks we draw near to Him and stay alert!
Evangelism (3-6): One key topic for prayer is evangelism. Divine intervention is indispensable for the spread of the gospel. Hence, even the Apostle asked for prayer. God alone can open a door for the Word. He alone can enable a person to make Christ known. Also, the church at large can reach unbelievers ("outsiders"). Our everyday contact with them is an opportunity! We leverage it and "walk with wisdom," esp., in terms of what we talk about. A wise walk means a wise talk, full of spiritual flavor, always speaking of God's grace. The right response to an outsider is much easier when we're ready with grace.
 Time with the holy God in prayer keeps us spiritually alert. The Lord gave the disciples a similar twofold command at Gethsemane: "Keep watching [same Greek verb as Col. 4:2] and praying" (Matt. 26:39-41).
 Thanksgiving is to ever attend our prayers. It is the mode of prayer as it was the mode of life in 3:15-17.
 NASB's "make it clear" is better rendered as "make it known [pha-ne-ro-ō (φανερόω)]" (NET). The gospel is veiled/incomprehensible to the unbelieving (2 Cor. 4:3-4) until God opens their eyes (Acts 16:14; 26:17-18).
 "Making the most of" is ex-a-go-ra-zō (ἐξαγοράζω) which means to buy out something. Like shoppers on Black Friday, we aggressively take advantage of the opportunity that God gives us to proclaim Christ.
 "Conduct yourselves with wisdom" is literally "walk with wisdom." This is a wise walk before outsiders.
 "Seasoned with salt" means flavor. It parallels "with grace [God's grace]." Grace is the flavor in our message.
 "Seasoned" is a perfect participle which shows seasoning is done and ready. This speaks of preparedness.