The prophet Isaiah tells us that “he who walks righteously and speaks uprightly” is also he who “stops his ears from hearing of bloodshed and shuts his eyes from looking upon evil” (Is. 33:15-16).
In the Wisdom of Sirach we are told to “hedge in thy ears with thorns, hear not a wicked tongue” (Sir. 28:24). Advancing to the New Testament, St. Paul warns: “Do not be deceived: bad company ruins good morals.”
(1 Cor. 15:33). When addressing the church at Thessalonika he exhorts to “keep away from any brother who is living in idleness and not in accord with the tradition that you received from us” (2 Thess. 3:6). In his epistle to the Galatians he invites us to treat as accursed (ανάθεμα) anyone preaching a gospel contrary to that of the apostles (Gal. 1:8). Needless to say, this is someone whose openness to foreign or wicked ideas and conversation has definite, hard limitations.