What does Psalm 16:4 mean?

Contrast between believers and unbelievers is a running theme in Scripture. In the prior verse, David expressed delight in the saints (Psalm 16:3), but here he refuses to participate in false faiths. Although Israel was called to be holy as a nation, not everyone in the land was holy. Many were idolaters. They worshiped "another god" and performed drink offerings to these false deities. David predicts they will experience an increasing number of sorrows.

Although New Testament believers are commanded to demonstrate love for unbelievers (Matthew 5:44; 22:36–40), they must not love their sin (1 Thessalonians 5:22). Second Corinthians distinguishes believers as the temple of the living God (2 Corinthians 6:16). As such, believers must not become "unequally yoked with unbelievers" (2 Corinthians 6:14). The same passage commands believers: "Therefore go out from their midst, and be separate from them" (2 Corinthians 6:17).

Although Lot was a believer, he chose to form close ties with the wicked Sodomites (Genesis 13:12–13). He moved into Sodom and rose to prominence there, but ultimately lost everything he possessed when God judged Sodom (Genesis 19:15–16). He was fortunate not to join the ultimate end of those whose "sorrows…shall multiply."