"Do not give what is holy to the dogs; nor cast your pearls before swine, lest they trample them under their feet, and turn and tear you in pieces." (Matthew 7:6)
Commentary: "The ...lesson contained in this passage, is the importance of exercising discretion as to the person with whom we speak on the subject of religion. Everything is beautiful in its place and season. Our zeal is to be tempered by a prudent consideration of times, places, and people. "Don't reprove a scoffer," says Solomon, "lest he hate you." (Prov. 9:8.) It is not everybody to whom it is wise to open our minds on spiritual matters. There are many, who from violent tempers, or openly profligate habits, are utterly incapable of valuing the things of the Gospel. They will even fly into a passion, and run into greater excesses of sin, if you try to do good to their souls. To name the name of Christ to such people, is truly to "cast pearls before swine." It does them not good but harm. It rouses all their corruption, and makes them angry. In short, they are like the Jews at Corinth, (Acts 18:6,) or like Nabal, of whom it is written, that he was "such a worthless fellow, that a man could not speak to him." (1 Sam. 25:17.)
This is a lesson which it is peculiarly difficult to use in the proper way. The right application of it needs great wisdom. We are most of us far more likely to err on the side of over-caution than of over-zeal. We are generally far more disposed to remember the "time to be silent," than "the time to speak." It is a lesson, however, which ought to stir up a spirit of self-inquiry in all our hearts. Do we ourselves never check our friends from giving us good advice, by our moroseness and irritability of temper? Have we never obliged others to hold their peace and say nothing, by our pride and impatient contempt of counsel? Have we never turned against our kind advisers, and silenced them by our violence and passion? Alas! we may well fear that we have erred in this matter." - JC Ryle
"Hence it is evident, how grievously the words of Christ are tortured by those who think that he limits the doctrine of the Gospel to those only who are teachable and well-prepared. For what will be the consequence, if nobody is invited by pious teachers, until by his obedience he has anticipated the grace of God? On the contrary, we are all by nature unholy, and prone to rebellion. The remedy of salvation must be refused to none, till they have rejected it so basely when offered to them, as to make it evident that they are reprobate and self-condemned, as Paul says of heretics, (Titus 3:11.)" - John Calvin