In I Chronicles 12, we read of those who stood by David when Saul was persecuting him. It was easy to join David after he had become king. But here we read of people who joined him at a time when he was rejected and being hunted for his life. It's easy to live totally for the Lord in heaven but quite another matter to follow Him totally here on earth where He is rejected and despised. In the same way, it is easy to join a church after it has become famous and popular, but quite another thing to join it when it is despised, because you see that the anointing is there.
The men who became David's army generals later were those who followed him at a time when he was being persecuted by Saul and rejected by Israel. In our day also we see something similar. God raises up a man to do a work for Him in a particular place, but very few have eyes to recognize God's anointing on him and on his ministry. These few join him and don't care what 'Saul' or anybody else says about him. Thus they accomplish an eternal work for the Lord in their generation. We need to train our senses to recognize where the anointing of God is today.
A true servant of God will never be popular, even as his Master was unpopular. Jesus said, "Woe unto you when everyone speaks well of you, because they spoke thus about the false prophets. But blessed are you when all men speak evil of you, because that's how they treated all the true prophets." (Lk.,6:22,26) Very few people have understood this fact. A true prophet is almost never fully recognised or valued in his lifetime.
The history of the church shows that even the true apostles were rejected and despised by others in their lifetime. Paul was rejected by the believers in Corinth. He said in 2 Tim.1:15, "All those in Asia have forsaken me." Paul was true to God until the end of his life, but most of his fellow-believers forsook him. Jesus was true to His father and most people left Him too.
Some of the sons of Benjamin came to David when he was in a cave (12:16). David met them and told them "If you have come peacefully, my heart will be with you. But if you have come to betray me to my enemies - my conscience is clear - may God punish you." We have to be careful, because even today there are people who can come to us, pretending to be our friends. But if our conscience is clear, God will deal with them.
But look at the wonderful example of Amasai (1 Chronicles 12:18): "The Spirit of God came upon Amasai, who was the chief of the thirty valiant men, and he said, 'We are yours, O David. We are with you, son of Jesse. Peace to you and peace to him who helps you. Your God helps you. ' Then David received them and made them captains of his band". People like Amasai recognised God's anointing upon David, despite David's outward circumstances, because the Holy Spirit was upon them.
If you read the history of the church you will find that the truly godly men who stood against the established religious system in Christendom were always persecuted.
Look for the anointing of God upon a man - not for supernatural gifts (even Satan has supernatural gifts), but for the anointing and the grace of God - those are the proof that God is with a man. And if God approves of a man, we better approve of him too! Amasai had that much sense!