1. Once the Holy Spirit has taken up residence in a believer, that believer is sealed forever. The believer may fall into sin and even grieve the Spirit, but he is still sealed. He may even "quench the Spirit," but he is still sealed. 2. This seals shows both ownership and security--we who belong to God are His forever (see Eph 1:13, 13; 4:30; 2 Cor 1:21, 22; 1 Thess 5:19).