Whenever Paul introduced himself, he often said that his apostleship came "by the will of God" not man. He said that to save us from sin according to the will of God the Father, there was no other way than for Jesus to become our propitiation. 

Paul also said that his ministry came by the  will of God and in Jesus Christ. He realized  it was the perfect work of salvation and this is how he became a preacher of the true Gospel.

Paul tells us that God planned to make us "holy and without blame" [Ephesians 1:4]. These holy people without blame whom Paul spoke of do not refer to special class of people, but they refer to those who believe in the Gospel [or Good News] hidden in Jesus according to the will of God the Father. Therefore, those who have become saints united with Christ through the Gospel, God's gift of salvation are "the holy people" set apart from the people of this world

Referring to the saint the Apostle Peter said, "you are a chosen generation, a royal priesthood, a holy nation, His own special people" [1 Peter 2:9]. The saints who have been born again by believing in the Gospel are not of those who seek to attain their own moral ideals by building their own character, but they are of those who have been washed from their sins and sanctified only by believing in the grace of God alone. 

While the believers in the Gospel may seem ordinary, they are the special people who believe in the righteousness of God. In other words, those who have become saints before God not only have faith in the Gospel, but the roots of their faith are also united together in Jesus.