This episode occurs in Chapter 6, and is when Daniel has to find sanctuary very quickly after he insults a Roman soldier. He runs to the only place that he can go to in order to find sanctuary, which is Joel's house. However, Joel is not there, and it is only Malthace who is present, and she makes it very clear that Daniel is not welcome, as he will bring trouble into Joel's life. Note what Malthace says to Daniel when he tells her he must speak to Joel:
Nothing is so important as Joel's studies... If you cared anything about Joel, you woul dleave him alone. He can be a famous rabbi someday. He's not going to risk his whole future for a band of outlaws.
Malthace therefore refuses to greet Daniel hospitably because she fears her brother's attraction towards Daniel's revolutionary cause and ideals, and doesn't want her brother to jeopardise his future and potentially become involved in something that would place him in danger. It is only Daniel's sickness that causes him to stay in Joel's house and allows him to develop his relationship with Joel further.