Using their bible
(Matthew 24:23-26) 23 “Then if anyone says to YOU, ‘Look! Here is the Christ,’ or, ‘There!’ do not believe it. 24 For false Christs and false prophets will arise and will give great signs and wonders so as to mislead, if possible, even the chosen ones. 25 Look! I have forewarned YOU. 26 Therefore, if people say to YOU, ‘Look! He is in the wilderness,’ do not go out; ‘Look! He is in the inner chambers,’ do not believe it.
(1 John 2:18-23) 18 Young children, it is the last hour, and, just as YOU have heard that antichrist is coming, even now there have come to be many antichrists; from which fact we gain the knowledge that it is the last hour. 19 They went out from us, but they were not of our sort; for if they had been of our sort, they would have remained with us. But [they went out] that it might be shown up that not all are of our sort. 20 And YOU have an anointing from the holy one; all of YOU have knowledge. 21 I write YOU, not because YOU do not know the truth, but because YOU know it, and because no lie originates with the truth. 22 Who is the liar if it is not the one that denies that Jesus is the Christ? This is the antichrist, the one that denies the Father and the Son. 23 Everyone that denies the Son does not have the Father either. He that confesses the Son has the Father also.
(2 John 9-11)9 Everyone that pushes ahead and does not remain in the teaching of the Christ does not have God. He that does remain in this teaching is the one that has both the Father and the Son. 10 If anyone comes to YOU and does not bring this teaching, never receive him into YOUR homes or say a greeting to him. 11 For he that says a greeting to him is a sharer in his wicked works.