There are those who are inside Christ, through their obedience to the gospel, having been “baptized into Christ” (Rom. 6:3; Gal. 3:27). As Christians (those who are inside Christ), we have a responsibility to monitor how we behave and the influence we have upon those who are also inside Christ. But, the extent of our influence stretches beyond, into the realm of “those who are outside” of Christ.
God calls upon Christians to “walk in wisdom toward those who are outside” (Col. 4:5). Wise conduct of Christians among non-Christians (“sheep in the midst of wolves”) requires that we “be wise as serpents and harmless as doves” (Matt. 10:16). In similar fashion, God calls upon Christians to “walk properly toward those who are outside” (1 Thess. 4:12; cf. Rom. 13:12-14). Not only must we monitor our conduct, but we must also safeguard the appearance of our conduct (cf. 1 Thess. 5:21-22). There are many reasons for these instructions, but the main reason is that we should want those who are outside to come inside!