Saul had proven himself unworthy to be king of Israel because of his many acts of disobedience, so God rejected him.  Even though Saul still served as king, God had already chosen another man for his position.

God appeared to the old prophet Samuel and told him to go the house of Jesse to anoint a king.  Samuel protested that Saul would kill him, and he would have if he had found out.

Samuel invited Jesse and his sons to a sacrifice, knowing that God would reveal to him which son of Jesse would be anointed king.  Samuel first looked at Eliab and was certain this was the man God would choose as king.  But God had a message for Samuel that we also need to pay attention to.  "But the Lord said to Samuel, 'Do not look at his appearance or at his physical stature, because I have refused him.  For the Lord does not see as man sees, for man looks at the outward appearance, but the Lord looks at the heart.'" (I Samuel 16:7)  Eliab was evidently a handsome man who was tall and strong, but this did not matter with God.  He looks at the heart, the inner part of the person.

Isaiah prophesied that Jesus will be our judge on the last day and declares how He will judge us.  "And he shall not judge by the sight of His eyes, Nor decide by the hearing of his ears; But with righteousness He shall judge the poor." (Isaiah 11:3,4)  Jesus can look inside of us and see us for what we really are, so that we cannot hide anything from Him.  We need to  realize that we must get our hearts right with God so that when he looks in our heart it will be right with Him.

Jesse had seven of his sons pass by Samuel, trying to help him find the right one, but each was rejected by God.  Samuel asked if Jesse had another son.  Jesse said he did, but he was out taking care of the sheep.  The young man's name was David, and he was not even invited to the sacrifice.  He was the youngest, and someone had to take care of the sheep.  The one Jesse rejected was the one God chose, because "The Lord does not see as man sees."  God looked inside the heart of David and saw an exceptional and wonderful person.  He was one of the kindest and most generous people who ever lived.  David had a very special heart.  "I have found David the son of Jesse, a man after My own heart, who will do all My will." (Acts 13:22)  God was so impressed with the heart of David that he said it was like His own.  But notice carefully what it was about David's heart that made him special with God.  He said that David would "do all My will."  David was willing to obey all of God's will exactly as He delivered it.  God is still looking for hearts that are willing to give exact obedience to Him, but this has always been a rare quality.  He chose David as king because of it.  He will choose us for salvation.  "For to this end I also wrote, that I might put you to the test, whether you are obedient in all things." (II Corinthians 2:9)  God has always required exact obedience to His Word and still does today.