It was damn near law back then
isn't there sections in the bible that state it's the right thing to be married to more than one wife ?, (in the case that your brother dies)
sure, things are different, ... but how many of those religious preachers would change their minds about things if they started living the words of their book of scripture to such an extent ?
and don't let the prude "official wording" fool you, as I only know the words of the English translation, but when that accepted English translation say "went into her" they mean he
went inside her, only we don't say went, we say he came inside, or he did cum inside her.
But yes the brother was by law expected to have sex with his sister in law until he produced a child, at which point I think he could stop if he wanted to as the child would get his brother's name, maybe with Jr. added.
But really, the point it is, that there is no justification needed, as there are many many things people can do in their lifetime, and the
ONLY said actions and behaviors are wrong, or not right is because the behavior and actions are typically lied about. So it is important to remember how many things, actions, behaviors would be perfectly acceptable and
are when there is full disclosure. When people are completely honesty and can be trusted to voluntarily do the right thing, it opens the world up to many freedoms that were previously restricted.
After all, nearly every single law written (though there are certainly exceptions) were written because people could not be counted on to be responsible with the freedoms they were exercising
And who others engage in sex with, when it does not concern me or I am not involved in the relationship, is nowhere near within my rights to tell them what they can and cannot do, it is along the same lines as telling someone what religion they can practice.
But here it's like preaching to the choir