Ephesians 2:4–7 — But God, being rich in mercy, because of His great love with which He loved us, 5 even when we were dead in our transgressions, made us alive together with Christ (by grace you have been saved), 6 and raised us up with Him, and seated us with Him in the heavenly places in Christ Jesus, 7 so that in the ages to come He might show the surpassing riches of His grace in kindness toward us in Christ Jesus.
The believer's union with Christ is proclaimed in baptism - union in His life, death, burial and resurrection - but there is more!
As we close out this short series of reasons why we should reflect on baptism, we want to see that our union with Christ extends to the point where, since He is ascended to heaven and seated at the right hand of God, so is the believer. Since He is reigning, believers are seated with Him on His throne with Him, and since He is appointed Judge of all, they will also judge in Him.
First, see the passage above. It is a mystery, for sure, but Paul makes it very clear (using a tense that has a sense of an event having taken place in the past), that believers have been seated with Christ in the heavenly places "in Christ Jesus" - because of our union with Him. He uses the same tense in Romans 8:30 to indicate that those who are foreknown (fore-loved) by God have been glorified already! There is no doubt that the use of this tense at one level demonstrates the security of the believer and the certainty that these things will surely come to pass. But there is another sense in which they have already come to pass because we are in Christ and He is in us. Therefore, because He is seated at the right hand of God in heaven right now, so is every true believer. There is a solemn majesty and glory in these things, as we contemplate the work of Satan so completely undone in what Jesus Christ has accomplished - sinful wretches made clean and even now in Christ seated with Him in the heavenlies!
But again, there is more - our union with Chist extends still further. Elsewhere in Scripture there are indications that believers will have a role in judging angels and nations (1 Corinthians 6:2-3). And although it is implied in the believer's sitting with Christ as we saw above, Jesus even says in Revelation 3:21 that those who overcome the snares of this world will sit with Him on His throne, and will reign with Him - something that is confirmed in other passages (Revelation 22:5). How amazing! All of this comes about through our close and indissoluble union with Christ - and is something we need to reflect on in respect of baptism.
So, to summarize this series, we have seen that baptism should not be an event that happens once and is then forgotten. Believers need to cultivate the habit of reflecting on their baptism often, in order to enjoy all the blessings that are proclaimed in it - especially cleansing from sin, anointing with the Spirit and union with Christ. And unbelievers should see a clear sign of their need for cleansing and should hear a clear call to turn from their sins and trust in the Lord Jesus Christ each time they witness a baptism, or in their own baptism if they were then unbelievers and have still not come to Christ.