"Now, therefore, fear the Lord and serve Him with sincerity and truth; and put away the gods which your fathers served beyond the River and in Egypt, and serve the Lord." Joshua 24:14

Read verse 13 to see why the "therefore" begins this verse. A little bit of fright-fear of God is healthy for believers, but of course, reverential fear should dominate because He is our loving heavenly Father. Sincerity alone in what one believes is not enough. A person can be sincere, but sincerely wrong. Worshiping and serving God must be according to the truth; otherwise, there is no right or wrong way. God's creation tells us some things about God, and the Bible gives the detailed specifics. See John 17:17; "Sanctify them through Your truth: Your word is truth." What should the people do about their portable, pagan images? Get rid of them by destroying them, and then with singleness of heart serve the Lord.