In short, God tells him to marry a prostitute so that his life can become an object lesson.
Imagine young Hosea coming home one day and telling his parents: “Guess what? God called me to go into the ministry!” His parents beam with pride, until a bombshell is dropped on them, “…and he told me to hook up with a whore.”
That seems so inappropriate, ill-advised, and ungodly, yet that is what God says to do — and Hosea obeys.
The strangeness doesn’t stop there, however. When his hooker-wife gets pregnant, God tells Hosea to give the kids some unbecoming names. His daughter is given a name that means “not loved” and his second son, a name that means “not my people.”
This suggests that Hosea has reason to question who actually fathered his wife’s children.
Next, his wayward spouse splits, returning to her former way of life. So, God tells Hosea to go find her and take her back!
Although this chain of events was a horrific ordeal for Hosea, it is a profound object lesson for us: regardless of what we do, how badly we act, or how far we stray, God loves us unconditionally and pursues us relentlessly.