6 Do not give that which is holy (the sacred thing) to the dogs, and do not throw your pearls before hogs, lest they trample upon them with their feet and turn and tear you in pieces.
Matthew 7:6 AMPC
Guard what is holy
In the Old Testament, dogs were considered an unclean animal that the Jews would stay away from. Gentiles (people who didn't serve the God of Israel) were also called dogs as well. Jesus makes this statement when speaking to the Gentile woman in Mark 7:27.
Jesus wants us to protect or guard what is considered Holy. As Christians, communion is considered Holy to us because we do this ceremony in remembrance of our Lord Jesus. Only a Christian should partake in communion. Also in water baptism, we do this ritual (a religious ceremony of actions performed according to a command) when a person first comes to faith in Jesus. We only baptize people who have repented and accepted Jesus as Lord and Savior of their life. We see our example when Philip baptized the Eunuch.
36 And as they continued along on the way, they came to some water, and the eunuch exclaimed, See, [here is] water! What is to hinder my being baptized?
37 And Philip said, If you believe with all your heart [if you have a conviction, full of joyful trust, that Jesus is the Messiah and accept Him as the Author of your salvation in the kingdom of God, giving Him your obedience, then] you may. And he replied, I do believe that Jesus Christ is the Son of God.
Acts 8:36-37 AMPC
We can also look at this Scripture referring to ministries that God has given us. We would not give our ministry over to a non-believer because they would not value it. We value our service for the Lord and some people who have no respect for the Kingdom of God would trample over the ministry if we gave it to them.
Let us be mindful to guard and protect what is Holy.