Boundary lines are either real or imagined lines that mark the limits or edges of something and separates it from other things and places. In other words, it is a dividing line. When I was a kid, we'd play foursquare with a large rubber ball and four large squares marked out on the concrete with a piece of chalk. When the ball went over or touched the "line", it was declared out of bounds and it was a point for the one who did not get it out of bounds. The goal was to keep the ball in play without it going on or outside of those lines. I would see other kids playing marbles with similar rules. Circles would be drawn around a large marble in the middle. The kids would take turns shooting their marbles at the large, much desired marble in the middle, until one of them was able to get the marble to the outside of the circle. The goal was to retain as many of your shooter marbles as possible while also getting as many other marbles out of the circle - past the line. When you did, you claimed all those marbles as your own. We have all kinds of "dividing lines" in life, don't we? Some are quite real - like those drawn for the purposes of playing foursquare or marbles. Others are set up in our minds - not specifically clear to others, but definitely clear to us. The problem comes when someone wants to move one of those boundaries - stretching it or reducing it in some manner. We feel a little threatened, challenged, or overcome by this attempt to move the "markers", don't we?
Don’t stealthily move back the boundary lines staked out long ago by your ancestors. (Proverbs 22:28 MSG)
In Old Testament times, they did not have surveyors with highly technical laser point imaging tools to assist in laying out boundary lines. In fact, they'd use landmarks or "markers" of sorts to indicate a boundary. For example, they'd say the boundary limit was the mountain range to the east or the river to the west. If they had no such "visible" limit, they'd set up some kind of pile of stones or pillar. That "pile" would stand as a marker to indicate the point of boundary. As Moses divided up the land among the twelve tribes of Israel, he portioned out their "shares" and gave them these boundary limits. Some received lush land for farming, while others received the grazing lands rich with grasses and streams or wells. It was divided based on the needs of the tribes and their primary "business" or "trade" - farming, ranching, etc. When kings of old would attempt to expand their boundaries, they'd do so through military efforts, often taking into captivity the people of the regions they invaded and putting them into "service" for their own benefit - building up their coffers with the products of the captive's labor.
There are also boundary lines of different sorts which Moses gave Israel as they traveled with him through the wilderness and into the Promised Land. We often refer to these "boundary lines" as the Law of Moses - inclusive of the Ten Commandments, the specific instructions for the celebrations of Feasts and Festivals, the keeping of holy days, and the like. If you have been following me for any length of time, you will know I taught about the Commandments as merely "protective boundaries" in our lives. They were never meant to be "laborious" or "impossible" to keep, but were designed to assist us in remaining in a place of safety. This is all that God's "rules" really are anyway - like guardrails on a winding highway, they keep us safe from going over the edge!
It doesn't matter whether we interpret this passage literally as boundary lines establishing some matter of "ownership" of an object such as land, or as rules which help to keep us from going too far in the wrong direction - they are not to be moved! In other words, we cannot dispute the "ownership" of the land because the boundary lines establish that ownership. In the same manner, the boundary lines we choose to live within in our own lives often show who has been declared the "owner" of our lives! Live within God's boundaries and we are showing he is the owner of our life. Choose to constantly be moving those boundary lines and we reveal the ownership is really ours and not his. At first, this doesn't seem to significant, but we often move boundaries little by little, almost as though we'd hope nobody would notice them being moved. In truth, God catches each subtle movement of those boundaries and he is grieved when we push them away, or even "fudge the line" a little.
Learning to trust the boundaries God establishes for our lives is part of growing up in Jesus. Trusting him enough to stay within those boundaries is a matter of maturity - not moving those lines is a matter of obedience. Boundaries established early in our walk with Jesus are not meant to be moved later on - they may become clearer as we walk with him, but once established, they are to be honored. Just sayin!