I don't think that Going Outside the Camp is necessarily going out to witness to billions in this context by David Platt.
Many have said that Hebrews 13:13, going outside the camp, is going out to the world to evangelize.
Back then the camp was "religiously legal polity" of Judaism.
Exactly what was "the camp" from which the apostle exhorted the Hebrews to go forth? And what does it mean today?
Jesus Christ was cast out of the camp by the religious and political system of His day. The Jews casting out of Christ, anathematizing Him, condemning Him to a malefactors death, which must guide us when seeking to identify the modem counterpart of that "camp."
What is the replica of that today? There is still a religious and political system today, where men justify themselves before God and will push you out of their "camp" if you don't come into agreement with them.
The camp is all the systems of man in this world. The education system, the political system, the religious system, etc. The political and religious system executed Him outside their camp.
The camp is full of mixture and is a form of godliness denying it true power. Moses moved his tent outside the camp because of mixture (which is sin).
What is required of you to go outside the camp? To separate yourselves from self-justification and self-righteousness before God. It is a spiritual withdrawal from everything that is not of God. The ideaologies of the CAMP must not regulate your life in God, its friendship must not be sought and its politics should be of no concern of yours. Just like Jesus. You are a stranger and pilgrim here and you are to conduct yourself as a pilgrim passing through, using this world, but not abusing it. 1 Cor 7:31.
Today's CAMP, has a religious system, that would verily crucify the Lord all over again and they will do the same to you. You can know this because they deny Him his place in His Church.
Heb 13:12 Wherefore Jesus also, that he might sanctify the people with his own blood, suffered without the gate.
Heb 13:13 Let us go forth therefore unto him without the camp, bearing his reproach.
Heb 13:14 For here have we no continuing city, but we seek one to come.
"He contrasts with the Jews, who serve an earthly sanctuary, the Christians to whom the altar in heaven stands open, while it is closed against the Jews. As Jesus suffered without the gate, so spiritually must those who desire to belong to Him, withdraw from the earthly Jerusalem and its sanctuary, as from this world in general. There is a reference to Exo_33:7, when the tabernacle was moved without the camp, which had become polluted by the peoples idolatry of the golden calves; so that every one who sought the Lord went out unto the tabernacle of the congregation (as Moses called the tabernacle outside the camp), which was without the camp; a lively type of what the Hebrews should do, namely, come out of the carnal worship of the earthly Jerusalem to worship God in Christ in spirit, and of what we all ought to do, namely, come out from all carnalism, worldly formalism, and mere sensuous worship, and know Jesus in His spiritual power apart from worldliness, seeing that we have no continuing city (Heb_13:14)." JFB
The Camp of Men will always be polluted with Idolatries and Compromise.
The same reproach that Jesus bore, all His people will bear, who leave the "Camp". By contrast, you will not bear the same reproach as He bore if you stay in the CAMP.
If you truly seek the Lord, then take heed to Heb 13:13 and go outside the camp. Because that is where the Lord is.
Are you willing to bear His reproach?