Collateral blessing

Several regulations contained in the OT law are difficult to explain using reason. While many laws are immediately understandable (do not murder, do not commit adultery), others are more ambiguous in terms of explaining their reasonableness. For example the dietary laws are sometimes explained either as being religiously motivated, to prevent inter-religious contact or confusion with heathen practices or for reasons of health. With several laws even those explanations are not satisfactory. For example it is quite difficult to find a rational reason for the tassels on a cloak (Deut 22:12).
Such approaches are human-centred. They try to explain the law using the criteria of reason and human welfare. But is this a good Biblical hermeneutic? A more appropriate starting point for such an undertaking should be the purpose of Scripture, or more specifically, authorial intention.
An example to illustrate the interpretation of these laws is Deuteronomy 22:8. This regulation - as closer study will show - doesn’t prioritize human welfare. As we will see, that puts this law in close relation to the above mentioned. At the same time it contains some additional remarks regarding side effects. As thus it offers a clear interpretation concerning its application.
"When you build a new house, you shall make a parapet for your roof, that you may not bring the guilt of blood upon your house, if anyone should fall from it. (Deuteronomy 22:8 ESV)
Grammatically this verse consists of three main sentences and a conditional sentence at the end. The conditional sentence relates to blood guilt. It explains what could cause guilt. So the main concern of the regulation is to prevent blood guilt. It is not the primary concern of the regulation to prevent someone from falling off the roof.
In order to clarify this angle on the regulation, the circumstances must be explained. In general terms the regulation applies to the time when the people of Israel will enter the Promised Land. In the Land they will build new houses. The new house will stand on the Promised Land. If the new house was built without a parapet, this might cause someone to fall off the roof. This, as a result, brings blood guilt on the house, the house being the "cause" of the incident. What the law accomplishes is to prevent God's Land from being desecrated.
The primary aim is the preservation of that which belongs to God. The primary issue cause is not human welfare. The regulation is God-centred, not human-centred. This places it beyond human reason. Fulfillment of the law is not driven by reason, but by the desire to serve and honour God.
In doing so, a collateral blessing occurs. When the builder of the house abides by the law, when he cares about the preservation of God's property - he builds a parapet - as a side effect he accomplishes a measure of security for the people. First he obeys the commandment of God, and only as a consequence he cares about man.
What happens if we apply the result of this regulation (explained in depth) to the more ambiguous earlier mentioned laws? First and foremost the law demands obedience. If the law is fulfilled, as consequence of obedience a blessing will arise. On the other side the urge to find a reasonable explanation leads to an human-centred interpretation. According to such an approach it becomes reasonable to obey a regulation only if there is a good reason to do so, i.e. only if there is an advantage for man. The law is no longer a command from God. It has become subjected to human reason. And by the same token it has lost its benefit for man.