God called Hosea to marry a prostitute. While this might seem strange, it was for the purpose of illustrating a message to Israel. After her lifestyle change, after marriage and children, she left it all to go back to her old lifestyle. Hosea redeemed her, forgave her, and completely restored her in order to win her whole heart.
We may look down on someone like Hosea's wife for her former lifestyle, but we must understand that we are all guilty of "cheating" on God when we give our minds or hearts to anything other than God - be that our families, our entertainment, money, etc.
But, we don't have to live with a harlot's heart... God will make a new heart in us.
Scriptures used: Hosea 1:1-5; Jeremiah 2:17-20, 24; Proverbs 7:6-27, Psalm 14:2-3, Romans 3:9-18, Revelation 17, Psalm 51:10, Hosea 6:10; 7:8; 8:14; 10:1-2; 13:9; 14:1-9.