As we all know not everyone that speaks to us has the Spirit of God abiding in them. There are those sent from satan who masquerade as “angels of light” but are actually false prophets.
13 These people are false apostles. They are deceitful workers who disguise themselves as apostles of Christ. 14 But I am not surprised! Even Satan disguises himself as an angel of light. 15 So it is no wonder that his servants also disguise themselves as servants of righteousness. In the end they will get the punishment their wicked deeds deserve.–2 Cor. 11:13-15 (NLT)
We must always test the spirit and see if it acknowledges the Lordship of Jesus Christ. The devil knows that God exists and he knows the Scriptures better than we do. The Spirit that dwells in us will witness to us if a person has a kindred Spirit to ours. But if you are in doubt, you can always ask if they believe that Jesus shed His blood on Calvary for our sins. If they acknowledge that this is true and they acknowledge the Lordship of Jesus, then we have assurance that it is not a false spirit.
3 So I want you to know that no one speaking by the Spirit of God will curse Jesus, and no one can say Jesus is Lord, except by the Holy Spirit.—1 Cor. 12:3 (NLT)