“Beloved, do not believe every spirit, but test the spirits, whether they are of God; because many false prophets have gone out into the world.” (I John 4:1 NKJV)
In the previous verse (3:24) the Apostle John said that the presence of the Holy Spirit is proof of our salvation. But now he warns us to be careful that we do not mistake false spirits for the Holy Spirit.
Some people make the mistake of thinking that every “spirit” they come in contact is from God. The Mormons, for instance, claim that the reported appearance of angels to some of their early founders proves that their religion was inspired by God. Even if they really were visited by angels, however, this would still prove nothing. As John says, these “spirits” need to be tested. The messenger must be examined on the basis of his message. The Apostle Paul says:
“But even if we or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed.” (Galatians 1:8)
Therefore, whenever you feel inspired to do something, stop and consider whether God is the source of the idea or not. You can tell by examining the message that you will send to others if you follow through with your idea. If the resulting message supports the mission of the gospel, then it is from God. If it will work against the message of the gospel, it is not.