Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you. 2 Corinthians 6:17. OHC 258.1
The true Christian will not choose the company of the unconverted. If Christ is formed within, the hope of glory, we cannot enjoy the malarious spiritual atmosphere which surrounds the souls of the irreligious.... OHC 258.2
Your acquaintances who are utterly averse to spiritual things are not refined, ennobled, and elevated by the practice of the truth. They are not under the leadership of Christ, but under the black banner of the prince of darkness. To associate with those who neither fear nor love God, unless you associate with them for the purpose of winning them to Jesus, will be a detriment to your spirituality. If you cannot lift them up, their influence will tell upon you in corrupting and tainting your faith. It is right for you to treat them kindly; but not well for you to love and choose their society, for if you choose the atmosphere that surrounds their souls, you will forfeit the companionship of Jesus. By every means in your power seek to repress sin; but never for one moment give sanction to sin either by your deeds, your words, your silence, or your presence. Every time sin is sanctioned by the professed follower of Christ, his sense of sin is weakened, and his judgment thus becomes perverted.... OHC 258.3
The Lord Jesus cannot keep any soul who places himself upon the enemy's ground and surrounds himself with the society of those who prefer such conversation and conduct as is an offense to the God he reveres and loves.... OHC 258.4
Cling close to those who will have an uplifting tendency, whose souls are surrounded with a pure and holy atmosphere.... God will be nearer to your heart, more in your thoughts, because you have separated from the world and from influences that would lead you away from the truth, and you will be less compassed with the snares of Satan.18Letter 51, 1894. OHC 258.5