1 Corinthians 15:33 Do not be deceived: "Bad company corrupts good morals"
Proverbs 27:17 As iron sharpens iron, so one person sharpens another
Your friendship have the possibility of drawing you closer to Christ or pulling you away from Him.
Examine your friendships, ask: Does this person cause me to become more like Christ or less like Christ, in your thoughts, actions, and attitudes?
We are called to bring people to Christ, but if a friend is causing you to "corrupt good morals", then maybe it would be wise to limit your time with that person and find more friends that will "sharpen" you!