Discern what is true from what is false

1 Kings 13:11-19
The old prophet answered," I too am a prophet, as you are. And an angel said to me by the word of the Lord: Bring him back with you to your house so that he may eat bread and drink water."(But he was ling to him) So the man of god returned with him and ate and drank in his house.
In this critical time for Israel and Judah, the role of the prophets in vital. The need to discern what is true from what is false is most acute in the case of those who claim to speak for God. But even a lying prophets may sometimes speak and recognize the truth. The prophet from Judah is wrong to accept the old prophet's word when it contradicts God's own word to him.
Why?
May be the prophet from Judah were tied, or he believed that the word of the Lord is changed so the new one is better than the old one that he heard from the Lord by his own.
God's word never changed, his decree and his command are endure forever. There are true and false prophets speaking. All of us should discern what is true from what is false is most acute in the case of those who claim to speak for God.
Knowing the truth then we can discern the false words.
How?
Do my best to read and understand the world of God with Holy Spirit. Someone said it is the word of God said to him, be aware of it.