In our world, a deposit (a few dollars down) is a "good faith" agreement that we will at some point in the future complete the transaction by paying the full purchase amount. Because we live in an imperfect world things don't always work out, but the deposit means something nonetheless.
Now, in the economy (household) of God, what does a deposit guarantee? Well we know that unlike us, God never goes back on a promise. So when He makes a deposit it is more than just a "good faith" agreement. It is a "perfect faith" agreement because God is faithful to always keep His promises.
(Read Ephesians 1:3-14; esp. 13-14)
True faith in Jesus Christ (His life, death, resurrection, and ascension - with His accompanying promise to return) is the means by which we receive forgiveness of sins, the promise of eternal life, and the life-changing power of the Holy Spirit. But when Paul talks about the Holy Spirit as "a deposit guaranteeing our inheritance" what does he mean?
Well to be more specific, Paul calls the Holy Spirit "a deposit guaranteeing our inheritance until the redemption of those who are God's possession - to the praise of his glory." Does that make things a little clearer? No. Okay. Let's break it down a little more then.
The deposit, unlike too many of our "good faith" agreements, is a perfect guarantee (it will certainly take place) of our inheritance (eternal life with God) because the guarantee is made by God Himself!
Remember that in 2 Corinthians 1:20 Paul says, "no matter how many promises God has made they are 'Yes' in Christ." So God does not make idle promises. He answers "yes" to all His promises and He does so in the person of Jesus. He has in the past, and He will in the future.
Therefore, the Holy Spirit (who we receive by means of true faith in Jesus Christ) is a deposit (a "perfect faith" agreement from the One who remains faithful forever) guaranteeing (it will certainly take place) our inheritance until the redemption of those who are God's possession.
In other words, Jesus Christ will return. He will judge the living and the dead, and He will make all things new! It is most certain because God has promised it. And God never goes back on a promise.
But when will the inheritance be fully ours?
Paul says, "... until the redemption of those who are God's possession." So we are in a holding pattern, waiting until the day Jesus Christ returns as God's "yes" answer to yet another promise. But waiting until when? "... until the redemption of those who are God's possession."
This means that if Jesus Christ has not returned, then those who are God's possession have not yet experienced the "redemption" that is theirs through true faith in Jesus Christ. So that means there is work yet to be done.
God brings people to Jesus, as we bring Jesus to people. So if there are more people to be brought to Jesus, then that means you and I have more people to whom we must bring Jesus. This is what it means to be "On Mission with God".
So what are your thoughts? What do you think Paul means when he calls the Holy Spirit, "a deposit guaranteeing our inheritance until the redemption of those who are God's possession"?