Matthew 7:6

That the most holy things ought not to be offered indiscriminately to all persons. The earliest comment on this v. is in the 'Teaching' (Didache): 'And let no one eat or drink of your Eucharist, except those who have been baptised in the name of the Lord. For it is concerning this that the Lord hath said, Give not that which is holy unto the dogs.' This correctly apprehends the principle, which is, of course, capable of wider application. Gore well says, 'We are not to shriek the highest truths of religion at a street corner. We are to wait till people show a desire for the deepest things before we offer them religion. Such was the method of the early Church. It went out into the world. It let all the world see the beauty of its life... But it did not teach them the secrets of its life—its Creed, its Eucharist, its Prayers—till they were ready for them, and showed their readiness at least by enquiry.'

That which is holy] in its literal sense the flesh of the sacrifices. Metaphorically it stands for all that is most holy in Christ's religion, like the pearls below. Dogs.. swine] i.e. unclean and ferocious persons. They will trample on (i.e. revile and profane) what you offer them, and assail you with ridicule and blasphemy. While they are in this frame of mind, nothing can be done with them.