1 John 4:1 Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world.
Do you know the sound of your own voice within you mind? When those thoughts are yours you know it. Then there are those thoughts which you are not so sure about. The fact that we hear them gives us pause to examine them. Not that we believe them, nor where they came from, but they are still an echo in your mind. So if those thoughts are not your thoughts, who do they belong to and what is the significance?
John 5:39 Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
Search the scriptures for significance. Be diligent to seek the word of the Lord. If it is of God you will find documented evidence. The scripture will reveal the author. If it is of God then find relevance. If it is not of God, then praise God, declare the name of Jesus and quiet the voice.
John 10:4-5 And when he putteth forth his own sheep, he goeth before them, and the sheep follow him: for they know his voice. And a stranger will they not follow, but will flee from him: for they know not the voice of strangers.