"In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit, who is the guarantee of our inheritance until we acquire possession of it, to the praise of his glory."
We need to pause at this point to clear up something that has often been a cause of confusion. The word 'after' is used twice (in the AV) in 13, first in relation to the hearing of the word of truth, and then in relation to the sealing of the Holy Spirit. There is, however, no suggestion in the original Greek of any 'time-lag' in either the matter of hearing or of believing, and the verse would be more accurately rendered 'In whom, on hearing the Word of truth, ye trusted; and in whom, on believing, ye were sealed with the Holy Spirit of promise'. There is no suggestion that the sealing of the Spirit took place at a time subsequent to believing the word of truth, but rather at the point at which genuine belief took place. Interestingly, this is the same Greek construction as we have in Acts 19:1ff, in the account of the disciples at Ephesus whom Paul felt were lacking in something vital. He asked them, not 'Have ye received the Holy Ghost since ye believed?' (which would imply a reception of the Spirit some time after believing in Christ), but rather 'Did ye receive the Holy Ghost when ye believed?' or 'Did you receive the Holy Spirit on believing?' (the implication being that their believing was faulty and deficient). The general teaching of the New Testament leaves us in no doubt that the reception of the Spirit constitutes one's initiation into the kingdom of God (see, particularly, Romans 8:9b, 1 Corinthians 12:13).