The people of Christ, the last Adam, is the people of the End and the New Age, the people of the future as well as the seed of Abraham. It is also the people of the Spirit, who is a sign of the End. Indeed Paul calls the Spirit an arrabon (2 Cor. 1:22; 5:5; cf. Eph. 1:14) which has its closest modern parallel in hire purchase and the deposit system.

A deposit has two functions; it is both the promise of the full payment to be made in due course, and the first installment of that payment. Similarly the Spirit as an arrabon (RSV “guarantee”) is both the promise of the future inheritance and its first installment.

The same idea is conveyed when the Spirit is called the “first fruits,” the image coming from the harvest (Rom. 8:23). To live in the Spirit is thus partly to live in present enjoyment of a future inheritance and also to have the assurance of its coming fullness. The church is then the community of the future.

from Pauline Christianity