"And you were also included in Christ when you heard the word of truth, the gospel of your salvation. Having believed, you were marked in Him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance until the redemption of those who are God's possession-- to the praise of His glory."
In this short little introduction to Ephesians, Paul marks out the will of God for the salvation of men. Here, we see the fullness of the Trinity coming together for our redemption; We are marked (by the Father) in Him (Christ) with the promised Holy Spirit. It is the Father who draws us in through the Son by the Holy Spirit. The Father is the fisherman, the Son the rod, and the Holy Spirit is the hook that never lets us go. Because it is God working in all three aspects of salvation, the process is made perfect. Were salvation from men, salvation would fail. But thank God that salvation is guaranteed for those who believe and are sealed with the Holy Spirit!
And this then is the mark of salvation for every true believer: That even when you sin and stray from the path, The Spirit will convict you, Christ will forgive you, and the Father will always bring you back to him for the Father always disciplines his children. All three Persons work together in perfect harmony for our redemption. Do you believe it? But truly, truly, by faith it is so!