ON FALSE TEACHERS
By St. Nikolai Velimirovic (+1956).
Man is at war in this world. Continual is the battle and numerous are the enemies. Among the most dangerous enemies belong the false teachers. Only if the mind of man is directed toward the Living God will he be safeguarded from these dangerous enemies.
  False teachers are either as blind men or as thieves; first, because of their blindness they lead both themselves and others into destruction and second, because of their hatred and envy they intentionally lead others astray, and hand over both their souls and bodies to the fires of hell.
  The Lord Himself prophesied: Many false prophets shall rise, and shall deceive many\ (Mt 24:11). The apostle only confirms the words of his Lord. Both false prophets and false teachers will sow the seed of destruction among the people. These are “damnable heresies” by which some will deny their Lord Who redeemed mankind by His All-pure Holy Blood.
Many false teachers have already appeared and have sown many heresies, damnable as tares, throughout the world. Brethren, if you know those “damnable heresies” which the Holy Fathers condemned at the [Ecumenical] Councils, then you will be able to recognize the principle seed of poison, which the devil through his servants sow in the field, over which the Savior had sown pure wheat. But even if you know or, if you do not know, direct your mind toward the Lord, enclose your mind with the sign of the Cross, call to your assistance the Holy and All-immaculate One, the Theotokos, the chosen ones of God, and especially your guardian angel and do not be afraid. Along with these always ask the Church, and the Church, being more experienced and victorious against all falsehoods, will tell you what the truth is. For you are from yesterday and the Church is from time immemorial. Your memory is shorter than the memory of the Church:
 O Lord Jesus, Thou art the only Path, the only Truth, the only Life. O 
lord, do not permit that we be led by false teachers and to apostate ourselves from Thee. To Thee be glory and thatiks always. Amen.
To this should be added what St. Vincent of Lerins said in the 5* century: All possible care must be taken that we hold that Faith which has been believed everywhere, always, by all.
  How does Ecumenism measure up to this standard? It doesn’t. From a historical point of view, at least, one can assuredly say that Ecumenism was believed nowhere, never, by no one.  St. Vincent provides us with a truly Orthodox understanding of the true Catholic Faith in its response to a widespread, but erroneous doctrine: What if some novel contagion seek to infect not merely an insignificant portion of the Church, but the whole? 
 Then it will be the Christian’s care to cleave to antiquity [i.e. the Church’s ancient teaching], which at this day cannot possibly be seduced by any fraud of novelty.
Vol. 18, Issue 07-08 Orthodox – Heritage, 
http://apantaortodoxias.blogspot.gr/2014/09/on-false-teachers-by-st-nikolai.html