As a preparation for our life after the resurrection, our Lord tells us in the gospel how we should live here and now. He teaches us to be peaceable, long-suffering, undefiled by desire for pleasure, and detached from worldly wealth. In this way we can achieve, by our own free choice, the kind of life that will be natural in the world to come.
Through the Holy Spirit we are restored to paradise, we ascend to the kingdom of heaven, and we are reinstated as adopted children. Thanks to the Spirit we obtain the right to call God our Father, we become sharers in the grace of Christ, we are called children of light, and we share in everlasting glory. In a word, every blessing is showered upon us, both in this world and in the world to come. As we contemplate them even now, like a reflection in a mirror, it is as though we already possessed the good things our faith tells us that we shall one day enjoy. If this is the pledge, what will the perfection be? If these are the firstfruits, what will the full harvest be?
Basil the Great (AD 330-379), Holy Spirit 15, 35-36: SC 17bis, 364-370