Mat 7:15 "Beware of false prophets, who come to you in sheep's clothing, but inwardly they are ravenous wolves."
These false prophets are ravenous wolves, who teach and speak perverse things (heresies) to kill the flock by destroying their faith in His words. These destructive doctrines will always draw misled Christians to these wolves. This was prophesied two thousand years ago and today there are rampant all over the world.
Act 20:29-30 For I know this, that after my departure savage wolves will come in among you, not sparing the flock. Also from among yourselves men will rise up, speaking perverse things, to draw away the disciples after themselves.
Rom 8:5-6 For those who live according to the flesh set their minds on the things of the flesh, but those who live according to the Spirit, the things of the Spirit. For to be carnally minded is death, but to be spiritually minded is life and peace.
For these false prophets (agents of Satan) to destroy new Christians is easy, for all they need to do is to deceive them into gratifying their flesh again. A clean sow will happily revert to wallow in the mud again, so unlearned and carnal Christians will gladly accept these heresies and revert back to love the world again.
Ruler of this World
John 14:30 "I will no longer talk much with you, for the ruler of this world is coming, and he has nothing in Me."
Though God allows Satan to be the ruler of this world since the fall of Adam, He is still sovereign concerning His people and the devil cannot hurt nor harm us. So the devil uses this world to tempt, deceive and destroy our faith in Jesus and His words.
1John 2:15-16 Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. For all that is in the world—the lust of the flesh, the lust of the eyes, and the pride of life—is not of the Father but is of the world.
Know them by their Fruits
Mat 7:16-20 "You will know them by their fruits. Do men gather grapes from thornbushes or figs from thistles? Even so, every good tree bears good fruit, but a bad tree bears bad fruit. A good tree cannot bear bad fruit, nor can a bad tree bear good fruit. Every tree that does not bear good fruit is cut down and thrown into the fire. Therefore by their fruits you will know them."
Fruit of the Spirit - Imitate Christ
Eph 5:1-4, 5 Therefore be imitators of God as dear children. And walk in love, as Christ also has loved us and given Himself for us, an offering and a sacrifice to God for a sweet-smelling aroma. But fornication and all uncleanness or covetousness, let it not even be named among you, as is fitting for saints... For this you know, that no fornicator, unclean person, nor covetous man, who is an idolater, has any inheritance in the kingdom of Christ and God.
When we imitate our Lord Jesus, we will be filled with the love for one another and will manifest the fruit of the Spirit.
Gal 5:22-24 But the fruit of the Spirit is love, joy, peace, longsuffering, kindness, goodness, faithfulness, gentleness, self-control. Against such there is no law. And those who are Christ's have crucified the flesh with its passions and desires.
Bad Fruits of Wolves
Col 3:5-6 Therefore put to death your members which are on the earth: fornication, uncleanness, passion, evil desire, and covetousness, which is idolatry. Because of these things the wrath of God is coming upon the sons of disobedience
These worldly Christians are the sons of disobedience.