Deuteronomy — Chapter 19

He that went simply with his neighbour into the wood to hew wood, and the iron slipped from the handle, and the iron struck his friend. St. Gregory (10 Moral. 9): 'We go with a friend into the wood when we strive with a neighbour to know his faults; we hew wood simply when we rebuke sinners with pious intention. But the axe slips when the rebuke, harsher than necessary, is drawn into severity. The iron strikes the friend because the contumely uttered kills the hearer in spirit of charity. Such a one must flee to three cities—that is, must seek refuge in hope, faith, and charity.'

Thou shalt not take nor remove thy neighbour's landmark, which thy predecessors have set. The laws against removing landmarks apply morally to those who disturb the landmarks of Faith set by the Fathers and Councils—the boundary-stones of orthodox doctrine against heresy.