What does Matthew 7:6 mean?

Here again is a phrase from the Sermon on the Mount (Matthew 5:1–2) which most people, even non-Christians, have heard. The most common use of this comes from the King James translation, which warns not to "cast…your pearls before swine." It's easy to focus on the derogatory imagery of dogs and pigs and miss the real point, which is not meant as an insult. The message is about wasting things of value on those who not only won't appreciate them, but might even be angered by the offer.

The long-promised Messiah, Jesus, came to preach that the kingdom of heaven was near (Matthew 4:17). Those who believed this and followed Him were eager to tell this fantastic news to others. Of course, not everyone believed it. Israel's religious leaders, notably, would reject Jesus' claim to be the Messiah. They would accuse Him of heresy and blasphemy (Mark 14:61–65). What Christ said was true (John 14:6) and incredibly valuable (John 10:28), but the response of these men was rejection and hatred.

In Jewish culture, dogs were rarely pets. They were wild animals who roamed the streets in packs looking for food and attacking weaker animals. Dogs were symbols of immorality, barbarism, vulgarity, and ignorance. Pigs were officially unclean, according to God's law (Leviticus 11:7), and likely also scavenged for food. Pigs are voracious eaters, and not especially selective about food. Yet pigs can become aggressive when hungry; giving a herd of pigs something inedible when they expect food merely antagonizes them.

To be called a dog or a pig was a great insult in Jesus' culture. Still, He does not hesitate to compare those who reject Him as Israel's Messiah to dogs and pigs. Crucially, though, His purpose is not to degrade anyone. The emphasis is not on other people, but on God's people. This verse is a warning to Christians: don't waste time or invite harassment from those who are obviously hostile.

Scripture embraces the value of seeking to convince others of the truth (Matthew 28:19; 1 Peter 3:15; Acts 17:2). However, there is a difference between speaking to the willing, versus wasting time on the hard-hearted. In this verse, Jesus tells His followers to be aware of this difference. At times, we may not realize this until we've already tried to reach them (Matthew 10:14). Sometimes—such as pearls and pigs—we should know in advance that what we offer will be rejected. Spiritually speaking, "casting pearls before swine" isn't an act of love towards the unbeliever (Matthew 5:16); it's simply a waste of God-given resources.

Christ will give His disciples explicit instructions along these same lines, later in the gospel of Matthew (Matthew 15:14).