“Positive law” is a law that’s a law just because someone in power (God in this context) says so. It’s often contrasted with “natural law” or “moral law,” which are laws that are inherently right and wrong.
The law that we must drive on the right is a positive law. The answer could just as easily have been the left–as in England. Either choice is as moral as the other. Just so, the rule that tax returns are due April 15 is just an arbitrary date. April 1 would have been just as moral (and maybe appropriately ironic!)
On the other hand, driving recklessly or while drunk is not only illegal but wrong. It would be wrong even if the legislature had never made such rule.
When we interpret the scriptures, we should be very, very reluctant to find a positive law. If a conclusion is dictated by morality, then it’s clearly a matter of God’s will. We really don’t need the Bible to tell us that stealing is wrong. The Bible helps us in some more subtle areas, such as in sexual immorality, where our passions tend to cloud our judgment.
But on the whole, God’s morality is recognized by even non-Christians. The world considers it good to help the poor and hungry. The world considers it wrong to steal. Most people hate being lied to.
Thus, the moral teachings of the Bible educate us and help us be more sensitive to moral questions, but the moral law stands as true independently of the Bible. We are moral people because we are created in God’s image, and he has impressed his moral nature on us all.
On the other hand, there are some rules that even our greatest thinkers would never have figured out but for the Bible. Baptism and the Lord’s Supper fit this category, and yet these institutions are clearly expected of the church.
There are a few other issues that aren’t moral but which aren’t quite positive either.
Once you understand that we are saved to be part of a community that does good works, then the need to periodically assemble, to encourage one another, and to be equipped and built up is a very natural conclusion. On the other hand, the choice of meeting every Sunday is positive.
If you understand the nature of God and our salvation, then worship is the perfectly natural result. We sometimes constrain the spirit of worship by imposing a host of rules on what should be spontaneous–as were the Psalms, for example–and so we should worship because it’s our nature to worship, not because it’s commanded.
Just so, as the community has a mission, it really needs leadership. Choosing leaders who are spiritual and who’ve proven their spirituality in their lives and families is obvious.
I’m not sure that baptism and the Lord’s Supper aren’t the only positive laws. The Bible barely mentions Sunday (Acts 20:6; Rev. 1:10), for example, and these passages are far from commands.
And yet, except for a few Sabbatarian groups, such as the Seventh Day Adventists, the Christian community has universally adopted the practice of weekly, Sunday assemblies.
You see, there are many practices that are barely mentioned in the scriptures, but which are clearly of apostolic origin, that the modern church has chosen to honor. It only makes sense as apostolic practices will usually be very wise. However, such questions cannot be salvation issue.
God nowhere commands us to meet every Sunday. Therefore, if we decide for spiritual reasons to meet on Saturday instead, we aren’t violating God’s commands. We will not displease God by such a choice.