The idea is that Samuel’s speaking to the house of Israel in verse 3, doesn't refer just to the end of the twenty years; he was doing it throughout this period. ‘If ye do return unto the LORD with all your hearts, then put away the strange gods and Ashtaroth from among you.
Look at the terms for discipleship in the second part of verse 3: ‘Put away the strange gods’ – in our case any worldliness, love of earthly things over the things of God. ‘Prepare your hearts.’ Search your hearts. Repent, of course. Pray for advance in the spiritual walk. ‘Serve him only.’ We have got to look after our homes and families, and make a contribution in the world in a civic sense, but we have to put the Lord first. ‘Serve him only’, not go all out for promotion and substance. And in those circumstances, as Christians, ‘he will deliver you out of the hand of the Philistines’, and in our case he will deliver us as his people out of the hand of Satan and the influence of Satan to oppress our work and prevent our progress.
I am reminded years ago, hearing a preacher in central London, and his appeal to the people was so shallow. It was a kind of sinners’ prayer appeal. You just pray to God, and you tell him that you believe in Christ, and that Christ died to take away all our sin, and ‘I repent of my sin’, all in a single word. You don’t say what that sin might be; you don’t lament your sin; you don't show any shame for it; you don't make any statement of wanting to be rid of it by the help of God. You don't acknowledge your responsibility for it, that it was deliberate and wilful sin. You simply say, ‘I repent of my sin’, and then the preacher said, ‘That means that a great work has taken place within you, and you are now born again.’ How lightly it is all dealt with! This is how to mass manufacture nominal believers, phony believers, who aren't really saved! But repentance in the Bible from the Old Testament to the New is always more profound than that. ‘Return unto the Lord with all your hearts.’ This is a serious matter. ‘Put away the old, and prepare [stand-up] your hearts unto the Lord and serve him, and him only, and he will deliver you out of the hand the Philistines.’