In the chapter previous to our text, Paul warns the brethren of being cheated through “philosophy and empty deceit” (2:8), legalism (cf. 2:11-17), “worship of angels” (2:18), and asceticism (cf. 2:21). “These things indeed have an appearance of wisdom” (2:23). However, there is no wisdom there.
He begins chapter 3 with the statement, “If then you were raised with Christ” (v. 1). He knows they had already been baptized into Christ, and raised with Him to walk in newness of life (cf. Romans 6:4). He is making a point, and a strong one at that. They should not get wrapped up in the things discussed in chapter 2. Instead, they should “seek” and “set (their) minds on” “things above.” When they died, and were raised, their lives were “hidden with Christ in God.” Because of this, they were no longer to seek earthly things. Paul rightly says in Galatians 2:20, “it is no longer I who live, but Christ lives in me.” In that way our lives are hidden with Him, and we should be seeking heavenly things.
If we continue to act like someone who has been “raised with Christ,” then “when Christ who is our life appears, then you also will appear with Him in glory” (3:4).