*Minor differences ignored. Grouped by changes, with first version listed as example.
In the midst of the boards - If we suppose the boards to have been of ordinary thickness Exodus 26:16, the bar was visible and passed through an entire row of rings. In any case, it served to hold the whole wall together.
And the middle bar in the midst of the boards shall reach from end to end. From east to west, as Jarchi interprets it; but this can only be said of the middle bar on the north and south sides of the tabernacle, for the middle bar at the west end was north to south: about this bar there is some difficulty, as that it is said to be "from end to end", as if that only was; whereas it is reasonable to suppose that the rest were so likewise; it may be, they might come somewhat short of reaching the end, whereas this did entirely; or rather the truer reason is, because the rest of the bars consisted of various parts; whereas this was a long bar of one entire piece, reaching from one end of the tabernacle to the other: likewise it is said to be "in the midst of the boards"; and the Jewish writers are generally of opinion, that it did not run along in rings as the other bars did, but the boards and planks being bored, this went through the thickness of the wood throughout; and in this they are followed by Arias Moatanus, Vatablus, Dr. Lightfoot, and others: but to this it may be objected, that the boards must be very thick indeed, even incredibly so, to admit of such a bore as to let in a bar of this kind, and is not so consistent with its being a portable house; and besides, when it was at any time taken down, in order to be removed, such a bar must give a great deal of trouble, and be in danger of being broke to pieces; besides, if it was thus covered in the boards, as it must be, what need was there that it should be overlaid with gold, as in the next verse? it is more probable, therefore, that it went not through the midst of the thickness of the wood, but in the middle of the length of the planks, and so expresses its different situation from the rest of the bars, which were at or towards the top and bottom of the planks, and this in the middle of them. It is not said of these bars, whether they were within or on the outside of the tabernacle; it is most likely they were on the outside, as Josephus (w) says they were; since they would not have made a good appearance within side, where they would have been always seen by the priests within, whereas being without they were covered with the curtains.
(w) Ut supra. (Antiqu. l. 3. c. 6. sect. 3.)
"And the middle bar in the midst of the boards (i.e., at an equal distance from both top and bottom) shall be fastening (מבריח) from one end to the other." As it thus expressly stated with reference to the middle bar, that it was to fasten, i.e., to reach along the walls from one end to the other, we necessarily conclude, with Rashi and others, that the other four bars on every side were not to reach the whole length of the walls, and may therefore suppose that they were only half as long as the middle one, so that there were only three rows of bars on each wall, the upper and lower being composed of two bars each.
*More commentary available at chapter level.