The apostle Paul had somewhat of the same idea when he said, "Having believed, you were marked in him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance. . . " (Ephesians 1:13) We have the Holy Spirit, the third person of the Trinity, inside of us, if we believe. A deposit means we have been marked "sold" or "put on lay away." We belong to God. No one else can have us (see also 1 Corinthians 6:19).
The Holy Spirit is given to us as a down payment, a deposit. That means there is more to come. A deposit or down payment is just the beginning. How much more Holy Spirit is there to come, how many more payments will there be? We don't know, but it will be fun to find out.
A deposit can also be like making a deposit in a bank. The bank wants to get as many deposits as possible so that it can use the money to make loans on which it charges interest and so makes money. We may want to get as much Holy Spirit into us as we can so that we can use the Spirits's gifts (make loans). Using those gifts, making those loans, comes back to us for our benefit also, just like interest does for a bank.
This down payment of Holy Spirit is also a guarantee. We are guaranteed the full inheritance of children of God, the largest inheritance of all.
Let us pray. Holy Spirit, you are so generous. I love that you have been deposited within me. I love your guarantee of the full inheritance.