The tree is known by its fruit

1. The tree that produces bad fruit is not good and the tree that produces good fruit is not bad, for each tree is known by its own fruit. Figs cannot be picked from thorn  bushes, nor can bunches of grapes be cut from briars. A good man brings forth good things from the good treasure of his heart, whereas the evil man takes evil things from the evil treasure of his heart, for the mouth  speaks from what fills the heart. (Lk. 6:43-45)

2. Beware of false prophets who come to you covered in the skins of sheep, but who on the inside are ravenous wolves. You will know them by their fruit.

Can grapes be picked from thorn bushes or figs from briars? Thus, every tree that is good produces good fruit and every tree that is bad produces bad fruit. A good tree cannot produce bad fruit, nor can a bad tree produce good fruit. Every tree that does not produce good fruit will be cut down and cast into the fire. Hence, you will know them by their fruit. (Mt. 7:15-20)

3. Take care  so that no one deceives you, for many will come in my name saying, “I am the Christ” and they will deceive many.

Many false prophets will appear who will deceive many people, and because iniquity will abound, the charity of many will grow  cold. But he who perseveres to the end will be saved.

Therefore, if someone  says to you, “The Christ is here, or the Christ is there,” do not believe him, for false christs and false prophets will appear and will perform great prodigies and amazing things to the point of deceiving the elect themselves if possible. (Mt. 24:4-5, 11-13, 23-24; Mk. 13:5-6, 21-22)