1 Paul, an apostle—sent not from men nor by man, but by Jesus Christ and God the Father, who raised Him from the dead -Galatians 1:1 BSB
The Greek word for “apostle” is apostolos which means one who is sent on a mission, an ambassador, commissioned with the message of the gospel by Jesus Christ.
Paul’s apostleship came directly from the Lord Jesus Christ Himself to go out and bring many from darkness to the Light of Christ.
15 “Go!” said the Lord. “This man is My chosen instrument to carry My name before the Gentiles and their kings, and before the people of Israel. 16 I will show him how much he must suffer for My name.” -Acts 9:15-16 BSB
The phrase “God the Father, who raised Him from the dead” substantiates the Sonship of Christ and His bodily resurrection.