Whether we realize it or not, we are all affected by the people with whom we spend time. Their attitudes, philosophies, language, and spirituality (good or bad) have a tendency to rub off on us, even if we don’t realize it. The Lord warns us about this in I Corinthians 15:33: “Be not deceived: evil communications corrupt good manners.” This isn’t true only for young people. It is true for believers of all ages. We might not want to think this could happen to us, but the Lord encourages us not to be deceived about this important principle.
David realized how important it was to surround himself with the right kind of spiritually minded people. His testimony was, “I am a companion of all them that fear thee, and of them that keep thy precepts” (Psa. 119:63). He intentionally chose to minimize the time he spent around the ungodly, or only somewhat spiritually minded, and to maximize his time around truly dedicated believers. Doing so gave him continual encouragement to walk after the Lord with a pure heart and not after the ways of the world.
The Apostle Paul must have embraced this principle for living too. As we look through his letters, it is easy to see the close relationship he maintained with many saints who were truly living for the Lord. Luke, Aquilla and Priscilla, Philemon, Titus, and Timothy are only a few he mentions with whom he had consistent fellowship. In contrast, neither Paul nor David spent a great deal of time with the lost, or ungodly, unless it was with ministry in mind.
We are not suggesting that believers cut themselves off from the unsaved or become hermits. We have instruction and examples to the contrary. We learn from II Corinthians 5:20 that “we are ambassadors for Christ” with the ministry of reconciliation or, in other words, the mission of sharing a clear gospel of grace with all that we can. Similarly, Ephesians 3:9 tells us Paul’s mission was also to “make (or help) all men see what is the fellowship of the mystery.” We too should share this goal of seeking to share with everyone the gospel of grace and the joyous news of God’s secret program of grace that is distinct from Israel and the Mosaic Law. source