"There is still the youngest," Jesse answered, "but he is tending the sheep." Samuel said, "Send for him; we will not sit down until he arrives." So he sent and had him brought in. —1 Samuel 16:11-12
Have you learned to recognize God's setup? This is what we find in John 6. When Jesus went so far as to say, "Unless you eat the flesh of the Son of Man and drink his blood, you have no life in you" (v. 53), that did it. "This is a hard teaching. Who can accept it? ... From this time many of his disciples turned back and no longer followed him" (vv. 60, 66). They could not have felt more justified in their disgust. The offense in some people's anointing is camouflaged by God's setup. This way people can rationalize and dismiss the person and feel completely justified.
Eliab, Jesse's firstborn, was a setup. This is surely the one, even Samuel thought at first. But fortunately, Samuel kept listening to that voice he trusted.
If we are not truly tuned in to the voice of the Holy Spirit, we can let any prejudice of our own charm us to miss the authentic. On top of this, God may well test us by allowing our prejudice to overrule when someone's outward appearance is not up to what we think should befit an anointed servant of Christ.
Once Samuel saw David, despite his young age and utter lack of experience, the Lord said, "Rise and anoint him; he is the one" (1 Sam. 16:12). How did Samuel know? I only know that he knew. He knew he was not deceived. But he would not have been able to supply evidence to Jesse or anyone else that would be totally convincing. The pain of being today's man is that you can't convince another person of what you see unless the same Holy Spirit shows them as well.
Excerpted from The Anointing: Yesterday, Today, Tomorrow (Charisma House, 2003).