"Sanctify them by the truth : your Word is the truth. As you sent me into the world, I too sent them to the world. And I sanctify myself for them, that they also may be sanctified by the truth." John 17. 17-19
The word sanctifier means "set apart". God wants to transform our intelligence (Rom 12: 2) and make us men and women whose way of being, thinking, appreciating things and situations is in harmony with what he is. same: light and love. This necessarily sets us apart from the world whose leader, Satan, is murderer and liar.
At our conversion, we are born to the divine life and receive the Holy Spirit. But it takes time for our reasoning, our reactions, our appreciations to be transformed by the work of the Spirit of God in us by means of his Word which is the truth. In contact with this Word, we better understand the thought of God with regard to all things and our way of seeing is transformed. Suddenly, our behavior in all circumstances changes.
The Lord, when He was on earth, always and everywhere manifested the characters of the one who sent Him. He came from heaven for this, fulfilling his mission to the complete satisfaction of his Father.
It is this mission that he entrusts to us, sending us into the world. He does not ask us to live in contemplatives or isolate ourselves in a hermetically sealed environment. He asks us to live in this world as witnesses of God, as he himself has been throughout his life as a man on earth.
Our behavior must therefore bring out the fundamental difference between the thought of God and that of the world. It is not a question of anything theoretical, but of our way of being in our family, in the family of the faith, and with all those whom we meet and who are not yet saved.
The world has an immense and dense network of communications to spread its reasoning, propose its criteria, impose its choices. Do not let us influence ! It is through the Bible and his Spirit that God communicates his way of seeing him !
Source (Pleasing the Lord)