In the name of the Father and of the +Son and of the Holy Spirit, Amen.
Saul had failed to do what the Lord had commissioned and commanded him to do. He was rejected by the Lord not because he was a sinner—he was that, but so are we. Not because he failed to believe—we all waiver of ourselves, but the Holy Spirit calls, gathers, and enlightens us in the Christian faith. So we all pray regularly, “Lord, I believe, help thou my unbelief.” No, Saul was rejected because he had been specifically authorized by the Lord, through Samuel, to do a certain task: to be the king, and follow certain commands. He didn’t do them. The more he departed from the Lord’s ways, the Lord’s commands, the Lord’s foreordained paths for him, the more he turned away from the Lord’s word. That was key. He turned away from the Word of the Lord. As in, he turned away from THE Lord, from the word of God who would later be made flesh to save sinners like you and me and Saul. But when you turn away from the Lord, from His word, from His judgment of your sin and His salvation of you from your just punishment, then there is nothing left for you.