Matthew 7:6

Give not that which is holy unto the dogs, neither cast ye your pearls before swine, lest haply they trample them under their feet, and turn and rend you.

Dummelow thinks this passage means "that the most holy things ought not to be offered indiscriminately to all persons."[1] In such a view, the dogs and swine would refer to mean and vicious persons who have no desire to apprehend spiritual things. This interpretation has come down from very ancient times. Clement of Alexandria said, "It is difficult to exhibit the true and transparent words respecting the true light to swinish and untrained hearers."[2] Another view is that the sacred abilities and powers of life should not be squandered upon the appetites and lusts of the flesh which can never be satisfied but which end by "rending" the giver. This, of course, is true, but is not necessarily what Jesus said here.

[1] J. R. Dummelow, One Volume Commentary (New York: Funk and Wagnalls Company, 1932), p. 649.

[2] Clement of Alexandria, The Stromata (Grand Rapids, Michigan: William B. Eerdmans Publishing Company, 1951), The Ante-Nicene Fathers, Vol. II, p. 312.