We ourselves, who have the firstfruits of the Spirit.--Romans 8:23 (ESV)
The word firstfruits refers to a tithe of sorts. Under Old Testament Law, the Jews brought the firstfruits of their harvest to God as an offering. It goes without saying that the actual harvest was much greater than the firstfruits. So it is interesting to me that Paul used the word firstfruits to refer to the Spirit's current indwelling. Paul seems to be saying, "Yes, this is good. The Spirit's gifts to us now are excellent. But when we cross over into eternity, there will be such a difference in our experience of God that this will be like just the tithe of the harvest." This is a remarkable truth, especially in light of the fact that this entire chapter is discussing the benefits which the Spirit brings to us. These benefits should impress us with God's grace and mercy to us. And yet, these are just the firstfruits of His favor on us. Paul goes through gift of grace after great gift of grace and then sneaks in one quiet phrase, "This is just the beginning."
This hope should increase our love for God and anticipation of Heaven all the more. Yes, the Lord has given us a taste of the glory of Heaven by His Spirit. At the same time, however, we should not be preoccupied with this world but instead be patiently waiting for an far greater outpouring of the Holy Spirit.