The gift of the Holy Spirit has a now/not yet aspect, as is seen in three New Testament metaphors:-
1. Commercial. The Holy Spirit is like the down-payment in a purchase. He is both the first instalment and the guarantee that the full payment will follow. 2 Cor 1:22; Eph 1:14.
2. Agricultural. The gift of the Sprit is like the harvesting of the first-fruits. It is both the beginning of the harvest and the gurantee that the rest will follow. Rom 8:23.
3. Social. The gift of the Spirit is like the first course of a banquet. It is both the foretaste and the guarantee of the meal that will follow. Heb 6:4f.
See Stott, Evangelical Truth, 128f.