Salvation only comes when we believe in Jesus Christ and the gospel of truth which is preached .we are saved by grace and not by works (Eph 2:8 ).We receive salvation when we believe in the gospel after hearing it. Then after believing ,we are marked with a seal ,a seal guaranteeing our inheritance until the final redemption . Consequently Faith comes by hearing .Faith therefore thrives on knowledge .For one to have Faith or believe ,he/she must first hear .This is recorded in Romans 10:17. 17 Consequently faith comes from what is heard, and what is heard comes through the preached word of Christ .
The sealing is as a result of believing and believing is as a result of hearing .This is how the book of Romans puts it .
Romans 10:14. 14 How are they to call on one they have not believed in? And how are they to believe in one they have not heard of? And how are they to hear without someone preaching to them?
Those who hear the gospel receive Faith which enables them to act on the word, because Faith means acting on what you believe.
A seal therefore is a device used to signify the genuineness of a document . It is used as an attestation of authenticity .In the ancient world if a person purchased goods of any kind ,it is marked with seal so that he might recognise it and be able to find it if mixed with other goods . The seal identified their owner and protected from theft .Paul metaphorically presents the seal to be the works of the HolySpirit in a believers life . Hence the Holy spirit becomes the seal of a believer (2cor 1:22 ). We are sealed by the spirit when we believe .The spirit becomes an attestation that we are spiritually validated ,genuine and protected as members of God’s family . By the Holy spirit we are now identified as christs and protected by him.we are ascertained to be the the children of God because God can never have a child who doesn’t partake in the holy spirit.