Upvote:1
Paul means do not be in a relationship with unbelievers such as marriage, business, or other situations where there would be pressure to compromise. That is different from being friends with unbelievers with a view to win them to Christ. Jesus himself quoted the Pharisees saying in Matthew 11:19 "The Son of Man came eating and drinking, and they say, βLook at him! A glutton and a drunkard, a friend of tax collectors and sinners."