"On Guard”

God through His word and His prophets, have given us sufficient warnings and to be on guard against false teachings.

Acts 20:28-29 AMP" Take care and be on guard for yourselves and for the whole flock over which the Holy Spirit has appointed you as overseers, to shepherd (tend, feed, guide) the church of God which He bought with His own blood. [29] I know that after I am gone, [false teachers like] ferocious wolves will come in among you, not sparing the flock;

Paul tells us as disciples of Christ we must be aware, expect and prepared for the attacks on God and His people(there's a war going on) false teachings inside the church will occur none will be spared.