Knowledge of God is not a philosophy or a logical system. All head knowledge puffs up, but this is the knowledge of God’s love and the Son’s salvation. It signifies freedom to serve. Christ gave his disciples a new commandment "to practice divine love in life by work and deed with prayer."
The disciples asked Jesus for protection and an added knowledge of God, when they understood, that he was to leave them. But Christ established them in the Father, so that they might be fitted to evangelize the world.
What was vital, was not their temporary cares about themselves, but their preparation for divine service. The knowledge of Father and Son saves us from egoism, and leads us into humble service. Jesus said: Whoever trusts in me works, does not just talk, but follows the path of sacrifice. To the extent that the believer denies himself and magnifies Christ, the Son who rose from the dead works in him and bestows heaven’s blessings on him. With such faith the Apostles were able to heal and to forgive sins as well as raise the dead in Jesus’ name after the outpouring of the Spirit. They denied themselves, and Christ lived in them. They loved him with all their beings, and glorified him in conduct.
Besides these holy ministries, Christ sent them to perform missions he had been unable to complete during his brief time on earth. After his ascension he sent his Holy Spirit, so that many might be renewed by their preaching. Children would be born to the Father, as dew falling at sunrise. Nothing is finer that our testimony given to the crucified and risen Christ. By trusting this witness, men receive life everlasting. The Holy Spirit comes upon those who cling to Christ and makes them God’s children, so that they magnify their Father all their life in uprightness.