We might say that baptism is the visible sign of the Spirit’s invisible work within us that tangibly shows God’s seal upon us and his promise to save in the gospel.

Paul speaks of the Spirit sealing believers in three texts (2 Cor. 1:21–22; Eph. 1:13; 4:30). While interpreters often associate this sealing with the down payment or guarantee of the Spirit, they tend to associate the “seal” with the Spirit himself as either a seal of authority or a pledge for full salvation. Others identify the seal with confirmation. And there are many other positions besides these.

My purpose here is not to dispute these conclusions but to point out how some Christians in the first centuries defined the seal of the Spirit as baptism itself.

In this article, then, I want to outline this historical position biblically and theologically and conclude by asking what such a view might mean for our baptismal practices today.

“Seal” in Scripture

The word “seal” in Scripture generally refers to a visible mark of ownership. As Mark Seifrid explains in his commentary on 2 Corinthians, “A ‘seal’ is a visible mark that signifies that a person or object is under the authority and protection of another.” And more concretely, it could be any sort of seal, such as a letter seal with the owner’s imprint upon it.

The term can be used in a variety of ways. Paul calls the Corinthians themselves the seal of his apostleship (1 Cor. 9:2). He also says circumcision was Abraham’s seal of righteousness by faith (Rom. 4:11). In Romans 15:28, Paul speaks of sealing the Greeks’ gift to the Jerusalemite Christians (though this does not come through in most English translations). So we can see that the NT writers use “seal” in a variety of ways.

The question we should ask then is not what does the word seal mean in general, but how does Paul associate the word seal with the Holy Spirit and baptism?

For example, Paul, in three places, identifies the seal as a key part of salvation, associated with the Spirit himself as our down payment:

• 2 Corinthians 1:21–22 (NIV): “Now it is God who makes both us and you stand firm in Christ. He anointed us, set his seal of ownership on us, and put his Spirit in our hearts as a deposit, guaranteeing what is to come.”
• Ephesians 1:13–14 (NIV): “And you also were included in Christ when you heard the message of truth, the gospel of your salvation. When you believed, you were marked in him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance until the redemption of those who are God’s possession—to the praise of his glory.”
• Ephesians 4:30 (NIV): “And do not grieve the Holy Spirit of God, with whom you were sealed for the day of redemption.”

Notice that in each case the seal associates closely with the Holy Spirit. Paul seems to identify the seal with the Holy Spirit (Eph. 1:13–14) but clarifies that the Spirit in fact seals us. What seems clear in Paul’s thinking is that the Spirit and seal are very closely identified; the Spirit seals us.

That does not yet answer the question of how the seal relates to baptism. So what made some early Christians make that connection?

“Seal” in Irenaeus

As I have explained in my article, “How the Early Church Baptized,” Christians understood water baptism to be the seal. The water visibly sealed the baptized by the Spirit to show that God had saved them and that the Spirit indwelled them through Christ. Irenaeus of Lyon (c. 180 AD) clarifies how early Christians made this connection.

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