The prophet's primary mandate is to declare what the Lord is saying, and help move the Body of Christ into a place of compliance to His kingdom purposes. At the same time, there are those who are not true prophets, but rather attempt to push their own agenda and purposes on others. You will only know the difference through the gift of discerning of spirits.
A true prophet is only concerned with God's will being done and manifested on earth, as it is in heaven. They cannot always explain the sense of urgency to see this happen, but as those who have their ear to the heart of the Father, they can only tell you what they are hearing, seeing, and sensing from Him. It is to the benefit and protection of the Body to listen to their voice, and heed their message with honor.
"Believe in the LORD your God, and you will be able to stand firm. Believe in his prophets, and you will succeed.” ~ 2 Chronicles 20:20b
"Yet the LORD sent prophets to bring them back to him. The prophets warned them, but still the people would not listen." ~ 2 Chronicles 24:19
"During this time some prophets traveled from Jerusalem to Antioch. One of them named Agabus stood up in one of the meetings and predicted by the Spirit that a great famine was coming upon the entire Roman world. (This was fulfilled during the reign of Claudius)." ~ Acts 11:27-28